Lyme disease is an infectious, multi-system, tick-borne disease caused by genospecies of Borrelia burgdorferi bacteria sensu lato, characterized by remarkable heterogeneity. In this situation choosing an optimal antigen array for diagnostic tests seems problematic. The serological tests for borrelia routinely done in laboratories often produce ambiguous results, which makes a proper diagnosis rather complicated and thus delays the implementation of an appropriate treatment regimen. Thirty-seven outpatients and eight inpatients with suspected borreliosis diagnosis hospitalized at the Clinics of the Pomeranian Medical University (Szczecin, Poland), participated in the study. In order to detect the antibodies against Borrelia sensu lato three kinds of serological tests were used: indirect immunofluorescence assay (IIFA), enzyme-linked immunosorbent assay (ELISA), and immunoblot. The IIFA and immunoblot tests conducted on 45 patients (100%) produced positive results for both the IgM and IgG antibody types. In the case of ELISA, positive or borderline results were observed in only 24 patients (53.3%). The immunoblot test for IgM most frequently detected antibodies against the outer surface protein C (OspC) antigen (p25), and, in the case of IgG, against the recombinant variable surface antigen (VlsE). The IIFA screening test used for diagnosing Lyme borreliosis produced the highest percentage of positive results, which were then confirmed by immunoblot, but not by ELISA. Therefore using only ELISA as a screening test or for diagnosing Lyme borreliosis seems debatable.