The aim of this study was to estimate the incidence of leukaemias and lymphomas in children according to the International Classification of Childhood Cancer third edition (ICCC-3) in the population covered by the Girona, Valencia, and Zaragoza population-based cancer registries and compare it with the incidence rates in other European countries. All haematological malignancies (HMs) registered between 1993 and 2002 in children below 15 years of age were included in the study. Pathological and haematological diagnoses were reviewed, recoded according to International Classification of Diseases for Oncology-3 and reclassified on the basis of ICCC-3. Sex and age-adjusted incidence rates were calculated, using the world population as standard. Five hundred and seventy-one HMs were registered in the Girona, Valencia and Zaragoza Cancer Registries during the study period. According to ICCC-3, precursor cell leukaemias were the most frequent HMs in children and constituted 60% of all HMs (an age-adjusted incidence rate of 42.7 per million children-years). The second most frequent childhood HM was Hodgkin lymphoma (11.2% of all HMs), yielding an age-adjusted standardized incidence rate of 6.3 per million children-years. With regard to myeloid lineage, acute myeloid leukaemias were the most frequent with a rate of 7.9 per million children-years. The standardized incidence rates for lymphoid leukaemia (1.19) and Burkitt lymphoma (3.94) were statistically higher than the rates observed in Europe. Compared with European data, Spain has a high incidence of lymphoid leukaemias and lymphomas. In particular, a high incidence of Burkitt lymphoma was observed. The causes of this geographical variation are still unknown.