Background: Determination of concentration of IFN-γ released from T lymphocytes upon stimulation with M. tuberculosis-specific antigens allows testing of cellular immune response in immunocompentent children who are infected with M. tuberculosis because of exposure to a case of active TB. ----- Aims: 1) to assess the influence of epidemiological factors on the concentration of IFN-γ, 2) to assess the influence of infectivity of adult source case on the occurrence of LTBI, 3) to investigate the impact of age on results of IFN-γ, and 4) to determine the agreement between IFN-γ and TST results. ----- Subjects and methods: We investigated children who had received compulsory BCG vaccination at birth because of history of exposure to a case of TB. TST was performed with two tuberculin units of standardized purified protein derivative (PPD) solution (Tuberculin PPD RT 23, Statens Serum Institute, Copenhagen, Denmark) by Mantoux method and transverse induration was measured 72 hours later. IFN-γ, using a commercial QuantiFERON-TB Gold In Tube test (Cellestis Ltd., Carnegie, Australia) was measured by ELISA method after the stimulation of T lymphocytes with M. tuberculosis-specific antigens (ESAT-6, CFP-10 and TB7.7). ----- Results: The results of the study demonstrate that the presence of cavitary lesions in adult source case, close contact with adult source case, AFB smear positivity status and positive culture status were associated with occurrence of LTBI in children. There was no evidence of age having impact on the concentration of IFN-γ. A moderate concordance between TST and IFN-γ was confirmed (85%, κ = 0,588). ----- Conclusion: Determination of IFN-γ may contribute to more precise diagnosis of LTBI in immunocompetent children less than five years of age, especially in children with discordant TST and IFN-γ results.