BACKGROUND:: Colorectal cancer surveillance guidelines rely on clinico-histological features of adenomas. Unfortunately, in common practice, recording of these features lacks precision and uniformity, which may hamper appropriate follow-up decisions. Confocal laser endomicroscopy (CLE) is a novel technology, that allows real-time in vivo microscopy of the mucosa and provides accurate histopathology. AIMS:: i) to define and validate differential features of adenomatous and non-adenomatous colorectal polyps by chromoendoscopy-guided CLE; ii) to assess predictive value of this technique for diagnosis of colorectal neoplasia. METHODS:: Patients at risk for CRC were prospectively investigated using CLE. During extubation, fluoresceine 10% was used in conjunction with acriflavine hydrochloride 0.05%, to characterize global tissue architecture, as well as cyto-nuclear features of colorectal epithelium. Ex vivo histology was used as gold standard. Reproducibility tests were performed. RESULTS:: In total, 116 colorectal polyps from 72 patients were examined. Ex vivo histology showed 68 adenomas, 6 invasive carcinomas, 30 hyperplastic and 12 inflammatory polyps. C-CLE of adenomas revealed lack of epithelial surface maturation, crypt budding, altered vascular pattern, and loss of cell polarity. In contrast, C-CLE of non-adenomatous polyps revealed epithelial surface maturation, minor abnormalities of crypt architecture and of vascular pattern, maintained cell polarity. Adenoma dysplasia score (ADS)reliably discriminated high-grade dysplasia from low-grade dysplasia (accuracy, 96.7%). Interobserver agreement was high (K coefficients: pathologist, 0.92, endomicroscopist, 0.88). In vivo histology predicted ex vivo data with sensitivity of 97.3%, specificity of 92.8% and accuracy of 95.7%. CONCLUSION:: C-CLE accurately discriminates adenomatous from non-adenomatous colorectal polyps and enables evaluation of degree of dysplasia during ongoing endoscopy. This technology may offer considerable potential to ultimately fine-tune surveillance programmes, particularly in high-risk groups.