BACKGROUND/AIMS: Advances in endoscopic technology seek to improve the accuracy of neoplastic tumor detection. Recently developed endoscopy devices such as narrow-band imaging (NBI) nevertheless have limitations in morphologic diagnosis. The purpose of this study was to investigate whether a novel imaging technique-near-infrared fluorescence (NIRF) imaging using a protease-activatable nanoprobe-could provide more accurate neoplastic tumor detection, compared to NBI. METHODS: Images of the intestines of Apc(Min/+) mice were obtained by NIRF using a matrix metalloproteinase (MMP)-sensing probe, which was based on a nanoparticle platform. Immediately after imaging, endoscopy with NBI capability was performed on the same excised intestine. Macroscopic and microscopic findings in the intestines were assessed, and MMP expression was analyzed by Western blotting and real-time polymerase chain reaction. RESULTS: Numerous tiny polypoid lesions were present in the intestines of aged Apc(Min/+) mice. These lesions included adenomas, lymphoid follicles, and protruding normal tissues. When using NIRF imaging with an MMP-activatable nanoprobe, adenomatous polyps showed higher fluorescence, compared to lymphoid follicles or adjacent normal tissues. The expression of MMP was higher in the adenomatous tissue than in the other tissues. The sensitivity and specificity for adenoma detection were 88.9% and 82.2%, respectively, when using NIRF imaging with a MMP-nanoprobe, compared to 77.8% and 66.7%, respectively, when using NBI (P<0.05). CONCLUSIONS: Near-infrared fluorescence imaging with a protease-activatable nanoprobe could aid in the differentiation of tumor characteristics. Clinical application of this approach may improve the endoscopic detection of neoplastic tumors.