To investigated the potential differences between probable and definite heterozygous familial hypercholesterolemia (HeFH) patients diagnosed by Dutch Lipid Clinic Network criteria. Clinical characteristics, lipid profile, severity of coronary artery stenosis and gene mutations were compared. Kaplan-Meier curve was performed to evaluate the cardiovascular events. Overall, 325 participants were included and divided into two groups: probable (n = 233) and definite HeFH (n = 92). Definite HeFH patients had higher low-density lipoprotein cholesterol (LDL-C), oxidized-LDL and proprotein convertase subtilisin/kexin 9 levels, and higher prevalence of tendon xanthomas. The incidence of genetic mutations was statistically higher in definite HeFH than probable HeFH patients. The coronary stenosis calculated by Gensini score was statistically severer in definite HeFH patients. The best LDL-C threshold for predicting mutations was 5.14 mmol/l. Definite HeFH had lower event-free survival rates. Definite HeFH patients had higher severity of phenotype and genotype, and higher risk of cardiovascular events.