Background. The aim of the present study was to analyse the expression of adhesion molecules in childhood non-Hodgkin lymphomas and to correlate the findings with clinical features and prognosis. Procedure. Samples were obtained from pleural and peritoneal fluids, bone marrow aspirates, and tissue biopsies from 21 patients (median age: 8 years). There were 9 T-cell and 12 B-cell lymphomas. The expression of CD18, CD44s, CD54 CD62L were investigated with flow cytometry by using monoclonal antibodies. Results. Absence of CD18, which was independent from immunophenotype, was found in 67% of patients. Positive CD44s and CD62L expression were observed in 48 and 63% of the cases, respectively. In ail of the cases with T-cell lymphoma, CD54 was negative, whereas 8 of 12 cases with B-cell lymphoma expressed this molecule (P = 0.005). There was no correlation between location of disease and the expression of adhesion molecules, except CD54 that was negative in all mediasten lymphoma (P=0.004). CD62L ( + ) patients had more frequently stage IV disease than CD62L ( - ) ones (P = 0.01). Two-year overall survival was 83 and 29% in CD18 ( + ) and CD18 ( -) cases; 55 and 36% in CD44s ( + ) and CD445 ( - ) cases; 46 and 42% in CD54 ( + ) and CD54 ( - ) cases; 42 and 50% in CD62L ( + )and CD62L ( - ) cases. Conclusions. The expression of LFA-1 on lymphoblasts is lost in the majority of childhood non-Hodgkin lymphomas. ICAM-1 is not detected on neoplastic cells of patients with T-cell lymphoblastic lymphoma. L-selectin positivity correlates with disseminated disease. There is no significant relationship between the expression of adhesion molecules and the survival rates, although CD18( + ) cases had better overall survival rate than CD18( - ) cases. Med. Pediatr. Oncol. 36:359-364, 2001. (C) 2001 Wiley-Liss. Inc.