Horizontal policy-making focuses on collaboration and cooperation to make the best possible decisions. There is a decreased focus on a traditional hierarchy of those with decision-making powers and a greater focus on the outcome of decisions involving new policies. Those involved in this process share the power of the decisions and take fairly equal responsibility for the process. Instead of focusing on competition, those involved in horizontal policy-making establish partnership as fundamentally important. They coordinate their efforts to determine how to best achieve their goals and how to involve affected individuals as part of the decision-making process. Because this involves a great deal of communication, research, and collaboration, this process can be lengthy.

In contrast, vertical policy-making looks much more like a hierarchy. There are individuals at the "top" of this decision-making pyramid who investigate issues and generate possible solutions. Those who will actually carry out those decisions are further down the pyramid and typically removed from the decision-making process. There are usually far fewer people who are involved in the decisions, and there is less focus on a sense of collaboration than exists in horizontal policy-making. While this type of decision-making typically produces faster results, the disconnect between those with the power to make decisions and those involved in the execution of those orders may produce less-than-desirable results.

The essential difference between horizontal and vertical policy-making is that in the former model, there is consultation between policy-makers at the same level, whereas in the latter model, policy is dictated from the top down. Horizontal policy-making is more democratic, and often more popular. However, it is also much slower. Various societies, such as the Roman Republic, have favored horizontal policy-making (debate in the Senate) in times of peace, but reverted to vertical policy-making (appointment of a temporary dictator) in wartime or in a crisis, when policies needed to be made and implemented quickly.

In practice, most policy-making is a mixture of horizontal and vertical elements. Occasionally, a president or CEO will decide on a policy alone and order everyone else to carry it out with no consultation. Conversely, in some communes or other small collective societies, every decision may be debated and voted on by the whole group. However, it is far more common for policies to begin with a small group at a high level, such as a committee in the Senate or the House of Representatives. These policies are debated horizontally before they are implemented vertically, and this may go on through several levels, with feedback as part of the process.

Vertical versus horizontal policy-making is a product of the nature of the organization involved in the process. Horizontal policy-making exists when departments or individuals within an organization of similar rank within the organizational hierarchy work collaboratively towards a common outcome. It is a more democratic process, in that many parties can be involved in formulating policy. It can also involve a considerably more protracted policy-making process, as there might be a requirement for a consensus to agree on the final decision. Getting all parties to the process to agree can require many hours of arduous negotiations or discussions with the final product representing, potentially, the optimal policy choice of none of the affected parties. The inevitable consequence of a democratic process such as is involved in horizontal policy-making is that the final decision reflects so many perspectives that it constitutes a watered-down agreement. That, however, is the nature of a democratic process in which no one party dictates policy to the others.

In contrast to a horizontal policy-making process, a vertical process is more of a "top-down" arrangement, in which policy is dictated from above and compliance is expected at lower levels of the organizational hierarchy. A vertical policy-making process may involve input or recommendations from the lower rungs of the organizational ladder, and research and analysis provided by those lower rungs may be instrumental in the upper level's decision-making process, but it is the upper ranks that ultimately make the decision and dictate the terms of that decision down the ladder. As such, vertical processes may be far less deliberative than horizontal ones, but decisions or policies can be made much faster, as the head of the organization is empowered to dictate policy. If speed is an issue, then a vertical policy-making structure is far more efficient. If compromise is desired and/or required, than a horizontal process may be more appropriate.

The difference between these two types of policy making is in the degree to which higher levels of government tell the lower levels what to do.  In a vertical policy making structure, the higher levels of government are able to pretty much dictate to the lower levels.  In a horizontal system, policy is made by a group of equals.  This distinction is typically seen in federal systems such as the US or the EU.

For example, then, immigration policy in the EU has historically been made horizontally.  Countries have worked together to formulate policy.  Recently, though, there has been a move towards a more vertical model.  In this model, the EU government tries to impose an immigration policy on the various member states.

The same thing happens in the US when the federal government takes more (or less) power over things the states do.  Right now, for example, the House of Representatives is proposing to let the states have more say in how they will run Medicaid.  This would be a much more horizontal system than the current vertical system.