OBJECTIVES: Correlate adenoid size as determined by lateral neck radiographs and intra-operative mirror exam. Determine if a radiologist's assessment of the lateral neck X-ray correlates with adenoid size. Assess the correlation of endoscopic findings to the degree of adenoid hypertrophy seen on intra-operative mirror exam. To perform a cost analysis of radiographic and endoscopic evaluations of the adenoids. STUDY DESIGN: Retrospective study. METHODS: Patients who underwent adenoidectomy were reviewed. The adenoid size as determined by the adenoid-to-nasopharyngeal (A/N) ratio, radiology report, and flexible nasal endoscopy were compared to the adenoid size as determined by intra-operative mirror nasopharyngeal exam. Compensation rates for each modality were compared. RESULTS: Sixty-one children had pre-operative airway radiography. Ninety-nine patients underwent flexible nasopharyngoscopy. When the A/N ratio was compared to the intra-operative mirror exam, the Pearson Correlation coefficient was 0.64 (p<0.0001). The radiology reading was compared to intra-operative mirror exam and the Spearman Correlation coefficient was 0.29 (p=0.0258). When endoscopic nasopharyngoscopy was compared to intra-operative mirror exam, the Pearson Correlation coefficient was 0.62 (p<0.0001). The cost of nasal endoscopy was $654. Lateral airway radiography plus radiology interpretation cost $605. CONCLUSION: Children who undergo lateral radiographs to assess adenoid size are younger than those who undergo awake flexible endoscopic nasopharyngoscopy. Both the A/N ratio and endoscopic nasopharyngoscopy correlate well with the findings of the intra-operative mirror exam. The radiologist interpretations that do not utilize the A/N ratio measurement do not correlate well with intra-operative mirror exam findings. Both modalities are comparable in cost.