BACKGROUND: Few studies have estimated the attributable risk and economic cost of mental disorders (MDs) due to particulate matters with aerodynamic diameter of <2.5Ê_m (PM(2.5)) exposure in Beijing. OBJECTIVES: This study aims to identify the possible correlation between PM(2.5) and risk of hospital admissions (HAs) for MDs in Beijing and calculate the attributable risk and economic cost. METHODS: A generalized additive model (GAM) with controlling for time trend, meteorological conditions, holidays and day of the week was used to estimate the associations. Stratified analyses were performed by age, gender and season. We further estimated the health and economic burden of HAs for MDs attributable to PM(2.5). FINDINGS: A total of 17,252 HAs for MDs were collected. A 10Ê_g/m(3) daily increase in PM(2.5) was associated with a statistically significant risk increase of 3.55% for HAs for MDs. The effects of PM(2.5) exposures on HAs for MDs were more pronounced in males, elderly (³65Êyears old) individuals and in cold seasons. Using WHO's air quality guidelines as the reference, 15.12% of HAs and 16.19% of the related medical expenses for MDs were attributed to PM(2.5) during the study period. NOVELTY: PM(2.5) accounts for substantial morbidity and economic burden of MDs for both the society and households, which shows environmental protections are essential to improve mental health status of the population.