The paper presents the method of scientific investigation of sacral architecture in the frontier region of Lithuania with Byelorussia and Poland. It also reveals the achieved results and highlights guidelines for future research. The investigation was supported by Lithuanian Science and Studies Foundation and completed in 2005. The paper describes the established criteria of architectural evaluation and prepared digital database of the main sacral structures. The present work covers the analysed features: the interaction of confessional building traditions, the influence of professional architecture on local architecture, the peculiarities of territorial dispersion of sacral buildings. Architectural and material composition, interaction of buildings with their environment and other sacral structures, symbolism and authenticity of 106 objects were investigated. The results of the investigation could be applied in recording of cultural properties and preparing of cultural heritage preservation projects.