Introduction: Individuals with neuropsychiatric disorders mostly increase smoking and tend to inactivity. But effects of changes in living habits and drug therapy on respiratory functions in patients with neuropsychiatric disorders are not clear. Our aim was to examine changes in respiratory functions in patients with neuropsychiatric disorders. Methods: Sixty-nine participants were enrolled in study (24 schizophrenia, 21 bipolar disorder and 24 healthy). Pulmonary functions were assessed with pulmonary function test, respiratory muscle strength as maximal inspiratory and expiratory pressures and dyspnea with mMRC dyspnea scale. Results: There were no difference in age and gender distribution and mMRC scores between groups(p>0.05) but BMI lower in healthy group [HG](both p<0.05). Smoke exposure was similar in bipolar disorder group [BDG] with other groups(p>0.05) but higher in schizophrenia group [SG] comparing HG(p=0.029). MIP and MEP were significantly decreased in SG and BDG comparing HG(p<0.001) but showed no difference between SG and BDG(p>0.05). FEV1, FEV1/FVC and PEF decreased in SG and BDG(p<0.05) comparing HG but similar between groups(p<0.05). FVC statistically decreased in SG(p<0.05) comparing other groups and BDG comparing HG(p<0.05). ERV, VC, IC and MVV were similar in all groups(p>0.05). Conclusions: Our findings showed that individuals with neuropsychiatric disorders may experience deterioration in their respiratory functions. However, it is reported that increase in smoking and decrease in activity in patients with neuropsychiatric disorders.  Our findings indicate that pulmonary rehabilitation may be favorable for those with neuropsychiatric problems.