Abstract Aim Non-cholesterol sterols reflect cholesterol metabolism. Statins reduce cholesterol synthesis usually with a rise in cholesterol absorption. Common hyperlipemias have shown different patterns of cholesterol metabolism. We evaluated whether cholesterol absorption and synthesis may differ after statin therapy in primary hyperlipemias. Main methods We determined lipid profile, apoprotein B and serum sterols (lathosterol, sitosterol, campesterol by gas chromatography/mass spectrometry) before and after statins in 80 untreated hyperlipemic patients, 40 with polygenic hypercholesterolemia (PH) and 40 with familial combined hyperlipemia (FCH). Key findings At baseline in FCH lathosterol was significantly higher while campesterol and sitosterol were significantly lower than in PH. After statins, the reduction in LDL-C did not significantly differ between the two groups; in PH there was a significant decrease of lathosterol from 96.1 to 52.6 102μmol/mmol cholesterol (p=0.0001) with no significant modifications in campesterol and sitosterol; on the opposite, in FCH lathosterol decreased from 117 to 43 102μmol/mmol cholesterol (p=0.0001) and campesterol and sitosterol significantly increased from 38 to 48 102μmol/mmol cholesterol (p=0.0001), and from 75 to 86 102μmol/mmol cholesterol, (p=0.022), respectively. After statin therapy only in FCH Δ-LDL-C showed a significant inverse correlation with Δ-sitosterol and with Δ-campesterol. Significance Primary hyperlipemias show different patterns of response to statins: in PH LDL reduction appears completely “synthesis inhibition” dependent, while in FCH LDL decrease appears to be synthesis dependent, partially limited by absorption increase. Studying cholesterol metabolism before and after hypolipemic therapy might be useful in identifying the best tailored treatment.