The analysis of eight cases of CAP (Community Acquired Pneumonia) was performed. The clinical samples of sputum were obtained from patients at which C. pseudodiphtheriticum strains were isolated in the quantity indicating the etiologic agent of infection. In two patients, K. pneumoniae and S. aureus were isolated simultaneously. They were considered as coexisting in the infection. C. pseudodiphtheriticum strains were highly susceptible to antibiotics. They were resistant to Erythromycin (87.5%), Clindamycin (87.5%), Lincomycin (75.5%), Trimeth./Sulfam.(37.5%), Chloramfenicol (37.5%). In the examined group of patients (five persons), the infection with C. pneumoniae was detected as recently passed or in progress with chronic character as the high level of specific antibodies (IgG or IgG and IgA) was present. That fact could predispose to infection with the opportunistic species of C. pseudodiphtheriticum. Of all the examined patients, three were infected with C. pseudodiphtheriticum as the only species responsible for infection (CAP).