Serrated polyps (SPs) are a heterogeneous family of polyps with distinct molecular underpinnings, clinicopathologic features and a varied capacity of malignant potential. They are new target lesions for endoscopists and pathologists, often underestimated and misdiagnosed. Due to their similar endoscopic and anatomopathologic characteristics a diagnostic overlap between hyperplastic polyps (HPs) and sessile serrated adenomas (SSAs) has been reported; nevertheless it is of utmost importance to correctly distinguish them since they have different malignant potential. The aim of this study was to evaluate the misdiagnosis rate of SSAs as HPs during a 8 years period (2006—2013) and the association between SSAs and other colorectal lesions. Methods: a retrospective, double blinded analysis of histologic specimens of all HPs diagnosed from January 2006 to December 2013 at Florence University Hospital was performed. The hospital database was consulted looking for association between SPs and other colorectal lesions. Results: after specimens revision of 2412 HPs the diagnosis from HP to SSA was changed in a 4,6% of cases (p=0,04). The change of diagnosis was assumed only if a 100% interobserver agreement was reached. SSAs resulted to be significantly more associated with other colorectal lesions (synchronous or metachronous) when compared with traditional serrated adenomas (TSAs) and mixed polyps (MPs). Conclusions: SSAs are more frequent than previously reported and are often misclassified as HPs (diagnostic overlap). The correct diagnosis of SSAs is important because they are the serrated polyps associated with a more rapid development of cancer and most associated with other colorectal lesions and other neoplasia.