To investigate late toxic effects of sulfur mustard (SM) on the upper and lower respiratory tracts of Iranian veterans, 43 male veterans with more than 25% disability due to SM poisoning in 20-25 years after exposure, were studied. Direct laryngoscopy, pulmonary function tests, arterial blood gasses and pH, computed tomography of sinuses and lungs were investigated. The patients were aged 50.6 (8.9 SD) years with body mass index (BMI) of 26.6 (4.0) and disability of 53.2 (17.0%). The common findings of the upper respiratory tract were dysphonia (79.1%), post-nasal discharge (PND; 41.9%), lower larynx position (30.2%), limitation of vocal cords (25.6%) and mucosal inflammation of larynx (14.8%). The common lower respiratory diseases were diagnosed as chronic obstructive respiratory disease (84%), bronchiectasis (44.1%) and lung fibrosis (7.7%). Severity of disability was negatively correlated with BMI (p = 0.032), spirometric parameters (p < 0.001) and oxygen saturation (p < 0.001), but positively correlated with low-density lipoproteins (LDL <0.010), blood pressure (p = 0.008), diabetes mellitus (p < 0.001), wheezing (p = 0.0043) and bronchiectasis (p < 0.001). Delayed toxic effects of SM in upper and lower respiratory tracts were mostly inflammatory and infectious complications, SM-induced disabilities were significantly correlated with risk factors such as diabetes mellitus, hypertension, LDL and lower-respiratory complications.