Objective To assess clinical characteristics, imaging and laboratory examinations for rheumatoid arthritis (RA) patients combined with interstitial lung disease (RA-ILD) and investigate related risk factors in RA-ILD. Methods Clinical data of 117 RA inpatients admitted by the Department of Rheumatology of Renji Hospital affiliated to Shanghai Jiao Tong University School of Medicine between July 2010 and July 2011 were retrospective analyzed. Clinical indexes such as age, gender, course of disease, history of active or passive smoking, medicine history, rheumatoid factors (RF), as well as anti-cyclic citrullinated peptide antibody (CCP) between RA group and RA-ILD group were compared and risk factors related to RA-ILD were analyzed. Lung high resolution CT (HRCT) images of RA-ILD patients were scored by using an international recognized scoring system to assess the severity of ILD. Correlations between the severity of ILD and above indexes were analyzed. Results Among 117 RA patients, 32 were males and 85 were females. 35 patients were diagnosed with RA-ILD (29.9%, 35/117). 4.3% (19/35) of patients had respiratory symptoms in the RA-ILD group. Ages and RA onset ages in the RA-ILD group were significantly older than those in the RA group (P=0.000 4, P=0.000 08). Proportion of active or passive smoking patients in the RA-ILD group was significantly higher than that in the RA group (P=0.001, P=0.005). Active smoking and passive smoking were independent risk factors in RA-ILD. The severity of ILD in male RA patients was greater than that in female RA patients (P=0.023 6). The onset of ILD was earlier in male RA patients compared with female RA patients (P=0.011 3). The older the RA onset age was, the quicker the development of ILD would be (P=0.004 2, r=-0.472 0). The severity of ILD in RA patients positive for anti-CCP antibody tended to be greater compared with RA patients negative for anti-CCP antibody (P=0.055 3). The severity of ILD was not associated with previous methotrexate or leflunomide administration (P>0.05). Conclusion We found, for the first time as far as we know, that passive smoking is an independent risk factor for ILD development in RA patients. Given that about half of RA-ILD patients only have slight respiratory symptoms, it is important to perform lung HRCT examination in order to achieve early diagnosis. Old age, male and positive for anti-CCP antibody in RA-ILD patients indicate more severe ILD and adequate attention should be paid to them.