BACKGROUND This study aimed to investigate the prevalence, clinical and radiographic features, and antibiotic responses of Mycoplasma pneumoniae (M. pneumoniae) infections in hospitalized adults with community-acquired pneumonia (CAP) in China. METHODS Serum specimens collected from 189 CAP patients in both acute phase and convalescence were tested for IgG, IgA, and IgM mixed antibodies specific to M. pneumoniae. The clinical and radiographic characteristics and efficacy of three antibiotic regimens were compared between patients with M. pneumoniae infection and those without. RESULTS Among 189 CAP patients, 88 (46.6%) were positive for M. pneumoniae infection. Compared to the negative patients, patients with M. pneumoniae infection were significantly younger, had higher rates of dry cough, and had white blood cell counts of <1010/L, but had less purulent sputum. Radiography further showed more centrilobular nodules, ground-glass opacities, tree-in-bud patterns and thickened bronchovascular bundles, but less pleural effusion and larger tracts of real opacities in patients with M. pneumoniae infections. Among the three regimens used, patients with moxifloxacin required significantly shorter fever abatement, treatment, and hospitalization times than those with azithromycin plus ceftriaxone and ceftriaxone only. CONCLUSIONS M. pneumoniae infection was present in almost half of the CAP population in east China, with some distinct clinical and radiographic features. Moxifloxacin was an effective antibiotic for this infection.