This article analyzes the spatial accessibility of primary healthcare services, i.e. the population's possibilities to receive healthcare services within an acceptable period of time in healthcare institutions situated in a certain territorial-administrative unit--the municipality. The aim of the study was to develop the technique for the quantitative evaluation of the spatial accessibility of primary healthcare services in different territories. The object of the study was the network of primary healthcare institutions and their subdivisions in the municipalities of Klaipeda, Taurage, and Vilnius districts. The methods of the study were geometrical modeling and applied graphics used for the quantitative determination of the ratios between the total zone area of the accessible primary healthcare institutions and the area of the respective municipal territory. The result of the study was the developed and proposed technique allowing for the evaluation of the spatial accessibility of primary healthcare institutions. The proposed technique of the evaluation of the spatial accessibility of primary healthcare services may be valuable in solving the problems of the development of primary healthcare institutions primarily in the rural regions of Lithuania. The quantitative expression of the evaluation could be used in decision-making related to investments into the development of the primary healthcare institution network in different administrational units of the country. The method of geometrical modeling involving the application of digital graphics may create preconditions for the creation of the geographical information system of the primary healthcare institution network in Lithuania.