Microbial infection and associated super antigens have been implicated in the pathogenesis of CTCL, and many patients die from complicating bacterial infections. It has been postulated that Chlamydophila pneumoniae infection may be involved in the pathogenesis of Mycosis fungoides (MF) but published data are limited and controversial. Aim of the study: The aim of the study was to analyze the frequency of C. pneumoniae DNA presence in blood samples of cutaneous T-cell and B-cell lymphomas (CTCL, CBCL) cases. Material and Methods: Using Q-PCR method we analyzed the presence of C. pneumoniae DNA in the blood samples obtained from 57 patients with CTCL (55-MF/Sézary Syndrome (SS), 1-primary cutaneous anaplastic large cell lymphoma (CD30+) and 1-NKT cell lymphoma) and 3 patients with cutaneous B-cell lymphomas and 120 individuals from control groups (40 patients with psoriasis, 40 patients with atopic dermatitis and 40 healthy controls). Results: C. pneumoniae DNA was identified in 13 of 55 cases in MF/SS group (23, 6%), in one patient with CD30+ large cell lymphoma and in 1 of 3 patients with B-cell lymphoma. The presence of C. pneumoniae was confirmed in 1 of 40 psoriatic patients (2, 5%), in 5 of 40 patients with atopic dermatitis (12, 5%) and in none of 40 healthy individuals. The frequency of C. pneumoniae DNA occurrence in MF patients group was strongly associated with the progression of the disease; rs = 0.756; p=0.0123 for groups IA→IVB, also for MF + SS patients divided by stages, the presence of C. pneumoniae was noted more frequently in advanced (III + IV) stages than in early (I-II) stages (p=0.0139). There are no differences in the main age of MF/SS patients with and without infection. Conclusion: Our results indicated that the presence of C. pneumoniae DNA in the blood cells is frequent event in late stages of MF/SS and may be explained by Th2 shift and suppression of immune system during the course of the disease.