Streptococcus pneumoniae is the most common cause of community acquired pneumonia. Pneumococcal infections are responsible for substantial morbidity and mortality worldwide due to the increasing rate of penicillin resistance. Therefore pneumococcal vaccine is highly recommended to the high risk groups. In this study, we aimed to investigate the antibody response to Pneumo-23 vaccine in high risk groups especially for the patients with asthma and chronic obstructive lung disease (COLD) and to detect IgG and IgG2 isotype antibody levels against the pneumococcal capsular polysaccharide antigens by ELISA method, in 41 patients aged between 44-85 years. Prevaccination IgG and IgG2 levels above threshold were determined in 83% and 51% of the patients respectively, whereas these rates have been detected as 93% and 90% respectively, one month after the vaccination. Immunologic response to the vaccine (seroconversion) was detected in 41% of patients for IgG and in 63% of patients for IgG2. Anti-pneumococcal antibody mean levels were found to be significantly higher after vaccination (p<0.05), and there were no correlation between age, sex, underlying diseases and hospitalization condition (p>0.05). In conclusion, pneumococcal vaccine might be beneficial to increase the level of preexisting pneumococcal antibodies and to protect the risk groups especially elderly people and COLD patients.