ObjectiveTo evaluate the diagnostic efficacy of Japan Narrow Band Imaging Expert Team(JNET) classification under narrow-band imaging (NBI) for colorectal laterally spreading tumors. MethodsData of 170 laterally spreading tumors (LST) detected by NBI and pigment dyeing were reviewed in the retrospective study. JNET classification under NBI was used for rediagnosis based on surface pattern and vessel pattern. Pit pattern(PP) was observed under pigment dyeing using PP classification. The results were compared with histologic results after endoscopic resection or surgery. ResultsThe diagnostic sensitivity, specificity, positive predictive value, negative predictive value and accuracy of JNET classification and PP classification were 922% VS 703%, 823% VS 850%, 747% VS 726%, 949% VS 835%，859% VS 797%, respectively (P=0159). The consistency rates of JNET classification and PP classification in predicting shallow invasion depth of LST were 61% and 83% respectively and the consistency rates in predicting deep invasion were 308% and 48%, respectively. ConclusionJNET classification under NBI is effective in predicting malignant laterally spreading tumors, however, its efficacy in predicting tumor invasion depth is unsatisfied. PP classification can be used to improve the diagnostic accuracy for those with diagnostic difficulty.