To determine the epidemiology of cancer among children from eleven Mexican states affiliated to Mexican Social Security Institute (Instituto Mexicano del Seguro Social, IMSS). 2663 Cases of children with cancer were prospectively registered between 1996 and 2002 in the main IMSS medical centers. The cases were classified according to the International Classification for Childhood Cancer. The general and specific cancer incidences (rate per million children/year, age standardized) were obtained. The principal groups of cancer in nine states were leukemias, lymphomas and central nervous system tumors (CNST). In eight states, the incidence was similar than reported worldwide (100 to 180); Chiapas had the highest incidence (203.5). Leukemias had higher incidence in seven States (>50). The highest incidences of CNST were observed in Chiapas and Guerrero (31.9 and 30.3); The incidence of neuroblastoma was low. Chiapas showed the highest incidence of retinoblastoma, bone tumors and carcinomas (21.8, 12.2 and 5.9 respectively); Puebla had the highest incidence of liver tumors (11.3) in which stages III and IV were the most frequent (67.8 %). The main groups of cancer in Mexican children were leukemias, CNST, and lymphomas. Some states had high incidence; more than 50 % of children with solid tumors were diagnosed in advanced stages.