The diagnosis of latent tuberculosis infection (LTBI) in Poland is difficult because of obligatory BCG vaccination and low specificity of tuberculin skin test (TST). Until recently, BCG vaccination was obligatory after birth and in 1., 6., 12., 18. year-olds respectively. Revaccinations are the cause of TST positivity for many years after vaccination. Specially threatened by M. tuberculosis infection are the risk groups which include the subjects staying in contact with the tuberculosis patients like: the close, casual and occasionally contacts. At present, the main role in diagnosis of LTBI, increasingly play the new tests which are based on measurement of interferon-γ (IFN-γ) which is released to the serum after stimulation by specific, mainly for tuberculosis, antigens. The aim of this work was to asses the prevalence of LTBI by in vitro test QFT-GIT and by TST in risk groups like: homeless, close contacts, casual contacts, nursing home pensioners and staff and in healthy subjects randomly choosen from the Crakow's population. The corellations between the results of the tests due to the age and gender of the subjects, between the concentration of IFN-γ in the serum and TST diameter and between the number of positive QFT-GIT results and TST diameter were assased. The agreement of the tests and kappa coefficients were analyzed and, by the same, the utility o ; f the QFT-GIT test in diagnosis of LTBI was assessed in testing risk groups in Poland. From July 2007 to September 2009 were diagnosed by QFT-GIT 785 subjects from the risk groups: 150 homeless, 171 close contacts, 163 casual contacts, 152 nursing home pensioners and staff and 149 healthy subjects randomly choosen from the Crakow's population. TST was assessed in 129, 156, 147, 148 and 121 subjects respectively. The special questionnaire about past and present diseases, habits, tbc contacts and symptoms, presence of BCG scar was performed. The physical examination was done to each subject. The QFT-GIT test was performed strictly according to recommendation of the producer (Cellestis, Carnegie, Australia). The blood of the subjects was taken to the three test-tubes: coated by specific antigens (ESAT-6, CFP-10, TB7,7), with positive control (phytohemaglutynin), and with negative control. TST (2 U Rt-23) was done on the same day and assessed on the third day by the same, experienced nurse. The result of QFT-GIT test (by ELISA) was established by the standard curve and software in the international units (IU). The concentration ≥ 0,35 IU/ml was interpreted as positive. The high incidence of positive results of QFT-GIT test in the tested groups was stated: in the homeless 37%, close contacts 27%, casual contacts 25%, in nursing home pensioners and staff group 21% an ; d in healthy 23%. The degree of infection was releted to the intensity of contacts with tb patients. There were observed characteristic positive correlations between positive results of QFT-GIT test and the age of the subjects, between the number of positive results of QFT-GIT test and TST diameter, weak and moderate correlations between concentration of IFNγ in the serum and TST diameter in tested groups. In each tested group with increasing TST diameter (cut-off 10 and 15 mm) the increasing agreement and kappa coefficients were observed, but never have achieved result more than moderate, so it is not possible to deduce about QFT-GIT result from TST diameter. QFT-GIT test characterized by high specificity should be performed in diagnosis of LTBI in so-called risk groups and in healthy population. The diagnosis of LTBI by TST is less usefull because of low specificity in BCG vaccination population like Poland. This test is characterized by low sensitivity in older people too. The further prospective investigations of the large risk groups are needed to answer the question who of the infection subjects with the positive result of QFT-GIT test should be the subject of profilactic treatment, which will get measurable results towards to the other subject with LTBI without treatment.