OBJECTIVES: To determine the value of narrowband imaging (NBI) screening for the early detection of head and neck squamous cell carcinoma (HNSCC) in patients who have received treatment and to assess the impact of radiotherapy on detection rates. DESIGN: Cross-sectional study. SETTING: Tertiary referral center. PATIENTS: From July 1, 2007, through February 28, 2008, a total of 206 patients with HNSCC underwent rhinolarynx videoendoscopic screening performed using conventional white-light and NBI systems during their routine postoperative sessions. MAIN OUTCOME MEASURE: The rate of detecting malignant tumors, depending on the anatomical site and stage of cancer and the history of radiotherapy after primary treatment. RESULTS: We identified 68 lesions by endoscopy in conventional white-light and/or NBI mode. Of these, 62 were histopathologically confirmed to be cancerous. The rates of detecting cancerous lesions by white-light and NBI modes were 100% and 97% for oral lesions, 69% and 100% for oropharyngeal lesions (P = .02), and 39% and 100% for hypopharyngeal lesions (P = .001), respectively. No difference was found between the 2 modes with regard to the detection of visible T1 to T4 tumors. However, NBI mode was significantly better than white-light mode for the detection of carcinoma in situ (P < .001). CONCLUSION: We found that NBI-assisted endoscopy is highly useful for the detection of precancerous lesions in the oropharyngeal and hypopharyngeal mucosa and is not affected by a history of radiotherapy in patients with HNSCC.