The aim of this study was to compare the clinical features of patients with elevated blood pressure and to detect variables associated with the diagnosis of primary hypertension. We identified 383 (69%) hypertensive children (197 [51.5%] with primary hypertension, and 186 [48.5%] with secondary hypertension) out of 553 children referred to our clinic with a history of elevated blood pressure. The primary hypertension group was significantly older and had higher BMI, positive family history of hypertension, and lower prevalence of preterm birth compared with those with secondary hypertension. No difference was found between the two groups in terms of the frequency of target organ damage. Multiple regression analysis showed that a family history of hypertension, obesity, age over 10 years, elevated uric acid, and presence of higher systolic blood pressure values at admission were independent predictors of primary hypertension; therefore, these parameters can be considered important clues for diagnosing primary hypertension.