Purpose: To explore the screening value of the adenoidectomy / nasopharyngeal (A/N) ratio from nasopharyngeal lateral radiography in children with obstructive sleep apnoea hypopnea syndrome (OSAHS). Methods: Children who had visited the respiratory department due to snoring and/or mouth breathing’ were enrolled. Nasopharyngeal lateral radiography and polysomnography (PSG) were performed. PSG monitoring is the gold standard for OSAHS. The differences in PSG monitoring results among different A/N groups were compared, and the correlation between the A/N ratio and PSG monitoring results was analysed. The receiver operating characteristic curve (ROC) was plotted to evaluate the screening value of OSAHS in children with the A/N ratio from nasopharyngeal lateral radiography to determine the diagnostic critical point. Results: A total of 425 children were enrolled. A total of 183 patients (43.1%) were diagnosed with OSAHS, including 113 cases (26.6%) of mild OSAHS and 70 cases (16.5%) of moderate to severe OSAHS. A total of 52 patients (12.2%) had an A/N ratio ≤ 0.60, 77 patients (18.1%) had an A/N ratio from 0.61~0.70, 142 patients (33.4%) had an A/N ratio from 0.71~0.80, and 154 patients (36.2%) had an A/N ratio ≥0.80 The patients with moderate-severe OSAHS had a higher A/N ratio than those with mild OSAHS and non-OSAHS. The OAHI, ODI, and the diagnostic rate of OSAHS were higher and the LSaO 2 was lower in the A/N≥0.80 group than in the other three groups. Spearman’s rank correlation showed that the A/N ratio was correlated with OAHI, ODI, and LSaO 2 (r=0.275, 0.227, -0.225, respectively). The area under the ROC curve for the diagnosis of OSAHS by the A/N ratio was 0.659, the critical value was 0.825, and the sensitivity and specificity were 45.1% and 80.9%, respectively. An A/N ratio ≥0.825 was identified as the main influencing factor of OSAHS by logistic multivariable regression analysis. Conclusion: There is a correlation between the degree of adenoid hypertrophy and OSAHS, and an A/N ratio ≥0.825 has good suggestive value for the diagnosis of OSAHS but is not a substitute for PSG.