Some of potential causes proposed to explain the reported increase of haematological malignancies in childhood during or after the war period in several countries include depleted uranium, chemical pollution and population mixing theory. The aim of this study was to define the population of Croatian children aged 0-14 years who were potentially exposed to each of those risks during the war and to investigate any possible association between the exposure and the incidence of haematological malignancies. The authors analyzed the data reported by the Cancer Registry of Croatia during the pre-war period (1986-1990), war period (1991-1995) and post-war period (1996-1999). In the group of 10 counties potentially exposed to depleted uranium and two counties where chemical war damage occurred, no significant difference in incidence of the studied haematological malignancies was noted in comparison to pre-war period. The incidence of lymphatic leukaemia significantly increased in four counties where population mixing had occurred during the war period, supporting the 'mixing theory'. In those counties, the incidence of Hodgkin's lymphoma decreased during and after the war. In Croatia as a whole, decreases in incidence of myeloid leukaemias during war and non-Hodgkin lymphoma after the war were noted.