The present study aimed to evaluate the relationship between OSA and adenotonsillar size in children of different weight status. A total of 451 patients aged 2-13 years with suspected OSA were retrospectively enrolled in the study. Correlations between the apnea-hypopnea index (AHI) and adenotonsillar size in different weight status were investigated. The adenoidal/nasopharyngeal (A/N) ratio of underweight children was significantly higher than that of normal-weight children (P = 0.027). Both adenoid and tonsil size were positively correlated with logAHI in children of normal weight (r = 0.210, P = 0.001; and r = 0.212, P = 0.001) but uncorrelated in the other groups. Gender (OR = 1.49, 95% CI: 1.01-2.20, P = 0.043), obese (OR = 1.93, 95% CI: 1.10-3.40, P = 0.012), A/N ratio (OR = 1.55, 95% CI: 1.28-1.88, P < 0.001) and tonsil size (OR = 1.36, 95% CI: 1.18-1.57, P < 0.001) were all associated with the severity of OSA. Adenotonsillar hypertrophy contributed to OSA in normal-weight children. In children of abnormal weight, instead of treatment for adenotonsillar hypertrophy, appropriate treatments for other factors are required.