Several international and national associations have proposed their own diagnostic criteria for metabolic syndrome. Regarding the heterogeneity of these guidelines, some authors refused the usage of metabolic syndrome definition. Here we aimed to analyze the differences between the diagnostic criteria proposed for metabolic syndrome. We reviewed and compared these different guidelines' criteria. We conclude that, despite the heterogeneity, there is a conceptual agreement on the definition of metabolic syndrome. But cut-off values and selection of diagnostic parameters are still conflicting. Diagnostic or definitive components of the syndrome (i.e., obesity, insulin resistance) should be considered separately from the associated-conditions (i.e., polycystic ovary, obstructive sleep apnea, microalbuminuria, non-alcoholic steatohepatitis etc.) of metabolic syndrome, during the course of diagnosis. Maintenance of the metabolic syndrome as a diagnostic category would still seem to be useful for an effective multiple cardiovascular risk prediction.