Objective To explore the diagnostic value of direct digital radiography (DDR, abbreviated as DR) lateral cephalometric films of the nasopharynx for adenoid hypertrophy (AH) combined with obstructive sleep apnea (OSA) in children, as well as its efficacy in assessing the severity of the disease. Methods A retrospective analysis was conducted on the clinical data of 100 children with suspected AH and OSA who were admitted in The Second Affiliated Hospital of Bengbu Medical University from February 2023 to February 2026. All the children underwent DR lateral nasopharyngeal radiography, and the adenoidal thickness (A) and the nasopharyngeal width (N) were measured, and the A/N ratio was calculated. A clinical symptom scoring system was established. The correlation between the A/N ratio and the clinical symptom score was analyzed, and the efficacy of the A/N ratio in predicting severe clinical manifestations of AH was evaluated using the receiver operator characteristic (ROC) curve. And the area under the curve (AUC) was calculated. Results A total of 100 children were divided into the surgical indication group (72 cases, including 46 cases of mild to moderate conditions and 26 cases of severe conditions) and the conservative observation group (28 cases). The A/N ratio and clinical symptom score of the surgical indication group were significantly higher than those of the conservative observation group (all P＜0.05). The A/N ratio was significantly positively correlated with the clinical symptom score (r＝0.802, P＜0.001). The ROC curve showed that the AUC of the A/N ratio for predicting severe clinical manifestations was 0.891, with the optimal cut-off value being 0.73, and the sensitivity and specificity were 84.6% and 85.1%, respectively. There was a significant difference in the A/N ratio between the mild to moderate and severe subgroups (P＜0.05). Conclusion The A/N ratio is highly correlated with the typical clinical manifestations of AH in children, and can effectively distinguish different clinical severities. The A/N ratio serves as an important reference index in the clinical assessment of AH and provides an objective basis for selecting surgical candidates.