In Poland, all forms of legionellosis are obligatory reported: Legionella pneumonia and extrapulmonary legionellosis (such as Pontiac fever). Total 210 cases caused by Legionella sp. were reported in years 2003-2010. In our study analysis of age, sex, place of residence of 163 patients with legionellosis reported in 2005-2009 were done. The majority (74.2%) cases were reported in Region Mazowieckie. Age and sex structure of patients in Poland in years 2005-2009 differ from the data of EWGLI. In Poland, legionellosis was much more frequently reported in children - 46.6% of the total reported, than in other countries. It might be a result of collaboration with the paediatricians during research conducted by our team in 2005-2007. Reported cases of legionellosis were also observed in 10 children aged < or = 2 years. Totally, legionellosis was observed more frequently among girls than in boys (M: F = 1:1,71), and in males (M: F = 1,64:1). It was also found that in smaller towns (< 100 thousand inhabitants) legionellosis was much more frequently diagnosed in girls (Po = 0.0152, 71.1% of ill children) and men (65.8% of adults). In larger cities (> 100 thousand.) differences in incidence between girls and boys and men and women were lower. To sum up: the number of reported cases of legionellosis depends largely on the availability of laboratory tests and the knowledge of physicians. Extension of diagnostic testing in the direction of Legionnaires' disease patients belonging to other than the high risk group increased number of detected cases, including those not so severe.