Objective To compare the distribution of bacterial strains and sensitivity to antimicrobial agents in cultured sputum from the senile dementia patients with community-acquired pneumonia (CAP) and with hospital acquired pneumonia (HAP) in order to provide a reference for clinical diagnosis and treatment. Methods A total of 132 senile dementia patients with pneumonia admitted in our hospital from July 2012 to December 2013 were enrolled in this study. Fifty-three of them suffered from CAP and the rest 79 from HAP. After their sputa were collected, the specimens were immediately inspected and cultured for microbial strains detection. The distribution of the obtained bacterial strains and sensitivity to antimicrobial agents were analyzed. The differences in pathogens, treatment and prognosis were compared between the 2 groups. Results The percentage of the patients suffering from CAP was 40.2% while that of those from HAP was 59.8%. The top 3 strains were Streptococcus pneumoniae (SPN), Staphylococcus aureus (SAU) and Haemophilus influenzae (HIN) for the dementia patients with CAP, and SAU, Pseudomonas aeruginosa (PAE) and Klebsiella pneumoniae (KPN) for those with HAP. In terms of antibiotic sensitivity, the most effective antibiotics against PAE were amikacin and aztreonam, those against KPN were piperacillin/tazobactam and imipenem, and those against SAU and SPN were vancomycin and linezolide. The condition was severer in the patients with HAP than those with CAP, and the incidences of complications and mortality were also higher in the former than the latter. Conclusion The patients of CAP group have no typical clinical manifestations, and most of them are hospitalized due to senile dementia’s symptoms, while those of HAP group are manifested with fever, attack of body function or consciousness. We should strengthen the clinical observation, improve the inspection rate of microbial cultures, and adjust the antimicrobials according to the results of susceptibility test to offer appropriate antibacterial treatment.