Structural unemployment involves a mismatch between the sufficiently skilled workers looking for jobs and the vacancies available.

Structural unemployment involves a mismatch between the sufficiently skilled workers looking for jobs and the vacancies available. Even though the number of vacancies may be equal to the number of the unemployed, the unemployed workers lack the skills needed for the jobs — or are in the wrong part of the country or world to take the jobs offered. It is a mismatch of skills and opportunities due to the structure of the economy changing. That is, it is very expensive to unite the workers with jobs. One possible example in the rich countries is the present combination of the shortage of nurses with an excess labor supply in Information Technology. Unemployed programmers cannot easily become nurses, because of the need for new specialized training, the willingness to switch into the available jobs, and the legal requirements of such professions.

Structural unemployment is a result of the dynamics of the labor market and the fact that these can never be as flexible as, e.g., financial markets. Workers are "left behind" due to costs of training and moving (e.g., the cost of selling one's house in a depressed local economy), plus inefficiencies in the labor markets, such as discrimination or monopoly power.

Structural unemployment is hard to separate empirically from frictional unemployment, except to say that it lasts longer. As with frictional unemployment, simple demand-side stimulus will not work to easily abolish this type of unemployment.

Structural unemployment may also be encouraged to rise by persistent cyclical unemployment: if an economy suffers from long-lasting low aggregate demand, it means that many of the unemployed become disheartened, while their skills (including job-searching skills) become "rusty" and obsolete. Problems with debt may lead to homelessness and a fall into the vicious circle of poverty. This means that they may not fit the job vacancies that are created when the economy recovers. Some economists see this scenario as occurring under British Prime Minister Margaret Thatcher during the 1970s and 1980s. The implication is that sustained high demand may lower structural unemployment. This theory of persistence in structural unemployment has been referred to as an example of path dependence or "hysteresis."

Much technological unemployment (e.g. due to the replacement of workers by machines) might be counted as structural unemployment. Alternatively, technological unemployment might refer to the way in which steady increases in labor productivity mean that fewer workers are needed to produce the same level of output every year. The fact that aggregate demand can be raised to deal with this problem suggests that this problem is instead one of cyclical unemployment. As indicated by Okun's Law, the demand side must grow sufficiently quickly to absorb not only the growing labor force but also the workers made redundant by increased labor productivity. Otherwise, we see a jobless recovery such as those seen in the United States in both the early 1990s and the early 2000s.

Seasonal unemployment may be seen as a kind of structural unemployment, since it is a type of unemployment that is linked to certain kinds of jobs (construction work, migratory farm work). The most-cited official unemployment measures erase this kind of unemployment from the statistics using "seasonal adjustment" techniques.