The PSP was a paramilitary police force under the jurisdiction the Ministry of Internal Administration. Its basic mission was the protection of property and public security in urban areas. Before its reorganization in 1953, the urban police had been under the control of provincial governors. During the colonial wars, security police assault units were dispatched to Africa, where they participated in combat operations against guerrilla forces. The PSP was reorganized and retrained in 1975, and its heavy equipment was turned over to the army.

PSP detachments operated from divisional headquarters in Lisbon and from the eighteen districts of continental Portugal, which were divided into North, South, and Central zones. There were also headquarters for Madeira and the Azores and sectional headquarters in smaller towns. Greater Lisbon and greater Porto had separate commands. A specialized traffic service shared highway patrol responsibilities with the GNR Traffic Brigade. A special group, the Intervention Police, had mobile sections poised for deployment anywhere in the country. Criminal investigation and data gathering was centralized under the General Anti-Crime Directorate, which employed 1,500 specialized officers and investigators. As of 1990, the PSP had a complement of 17,000 individuals. Staff was drawn from among former servicepersonnel. Since the early 1970s, women had also been recruited for plainclothes investigations and traffic control assignments.

In 1989, a demonstration by some 1,000 police personnel outside the Ministry of Internal Administration took a violent turn. The police had tried to form a union, but the government rejected the idea on grounds that the police, as a military organization, were prohibited by the National Defense Law of 1982 from having a union. The police maintained that they needed a union to improve working conditions marked by long hours and low pay. In the late 1980s, for example, an ordinary patrol officer earned the equivalent of only US$390 a month.

Data as of January 1993