Amyloid based hypothesis led to develop biomarkers oriented diagnosis of neurodegenerative dementias. Among them biomarkers for AD, the most diffuse form of dementia, are currently the unique available for scientific and diagnostic purposes. CSF biomarkers like Amyloid beta 42, total tau and phosphorylated tau levels can be easily evaluated in individuals suffering from cognitive decline, to diagnose or exclude AD type dementia, since early stages. Moreover, their analysis gave the opportunity to better understand cognitive decline patho-physiology during aging. Experience from their use and analysis however showed a high degree of variability due to the great heterogeneity of AD on one hand, the presence of isolated CSF biomarker changes that are not to be considered of AD type and deserve a clinico-pathological classification on the other. Aim of this review is to offer the knowledge about CSF biomarker’s use in clinics.