Glioblastomas are characterized by significant differences of neoplasms occurring in individual patients, as well as high heterogeneity of cell content within each tumor. The influence of photonic irradiation applied in different modes and doses on the cells of two new glioblastoma cell lines (T2 and R1) and long-studied lines of glioblastoma (T98G and A172) was investigated. In contrast to A172 and R1 cultures, in which all the cells died after exposure to relatively low radiation doses, in T98G and T2 lines a radioresistant cell population survived after higher doses of irradiation. This population was represented by large single or multinuclear non-proliferating growth-arrested cells. These cells remained viable for more than a month and in comparison with the intact cells were characterized by a multiple increase in the expression of genes encoding growth and proangio-genic factors, some extracellular matrix proteins as well as proteins connected with mesenchymal phenotype. The pattern of gene activity of growth-arrested irradiated T98G and T2 cells turned to be identical to gene pattern of the same cells treated with another genotoxic factor — fotemustine. Consequently, growth-arrested resistant cells in T98G and T2 glioblastomas actively expressed genes encoding the proteins that could affect both the tumor cells and their microenvironment.