We describe the rare coexistence at the time of diagnosis of Philadelphia positive chronic myelogenous leukemia (Ph+ CML) and non-Hodgkin's lymphoma (NHL). At the time of diagnosis, cytogenetic analysis of peripheral blood and bone marrow cells revealed the Ph chromosome translocation in all examined metaphases. The lymph node biopsy showed features of diffuse large B-cell lymphoma (DLBCL). This case may be of interest due to: (1) the rare coexistence of Ph+ CML and NHL at diagnosis, (2) the fact, that in contrary with previously reported cases in patients with antecedent or concurrent diagnosis of CML, where precursor lymphoblastic lymphomas are prevalent, in our patient clinical and laboratory findings revealed a diffuse large B-cell lymphoma, and (3) that the present case is an additional one confirming the poor outcome of patients with simultaneous occurrence of these two clinical entities.