Nowadays, the Ukrainian church building has not yet succeeded in establishing its own modern image/type of church, different from the conventional one. One of the significant reasons for this situation is the long break in the design and construction of churches in Ukraine during the 20th century. The Ukrainian diaspora has accumulated considerable experience in the construction of modern churches, which ensures the continuity of the tradition of the church building. The purpose of the research is to explore the still invaluable experience of designing church buildings and the architectural and artistic organisation of their interior in Ukrainian diaspora churches, which is an important foundation for solving the problem of developing the image/appearance of a modern church. The research used general scientific and special methods. Attention is devoted to the research of current issues of developing a light composition in the sacred space of modern diaspora churches. The research analyses several projects by architects of the Ukrainian diaspora in the field of sacred architecture. The research identifies the specific features of the establishment and development of church architecture in the Ukrainian diaspora in terms of the debate over the conventional and modern forms of church buildings and the spatial organisation of the light composition of their sacred space. The research outlines the influence of the local architectural tradition of the church building in North America – Protestant and Catholic churches – and the modernist design culture of the period of functionalism and neo-modernism in architecture on the architectonics of Ukrainian churches in the diaspora and the organisation of the light environment of their interior space. For the first time, the features and regularities of the organisation of the light environment of the most famous Greek Catholic churches of the Ukrainian diaspora in Canada and the United States, built in the second half of the 20th century, are explored. The influence of natural light on the architectonics of churches and the specific features of visual perception of their internal object environment and on the development of the appropriate mood imbued with mysticism and sacred atmosphere of the interiors of churches is determined. The experience of diaspora architects is explored and analysed, which has not been understudied but will be essential for use in the practice of Ukrainian architects in designing modern churches while preserving national identity and church-building traditions

In each historical period, light played an important mystical role in the creation of the sacred space of the temple, and was and is an integral part of religious ritual. Light is an architectural phenomenon, the formative and communicative element of the spatial structure of the temple, the most important factor in the perception of space and layout of the temple. The subject of the analysis contained in the article is the light environment in the space of modern churches of Ukraine. An analysis of the functions of light in churches is made on the example of recently built iconic Greek Catholic temples. The peculiarities of the distribution of natural and artificial light in the space of modern churches, the similarities and differences in the organization of the light environment, as compared to the historical temples, have been revealed. The influence of the light on the architectonics of temples and the visual perception of their object environment, on the formation of the corresponding mystical mood and sacred atmosphere is defined. The values and functions of electric lighting in the structure of the light environment of the temple, the directions of development of electric lighting systems due to the expansion of their utilitarian and decorative functions are determined.