The aim of this paper was to analyze the internal structure of two brief measures of personality, Big Five Inventory-15P and Big Five Inventory-10P, through SEM-CFA and ESEM, in 534 college students (77.5% females; Mage = 20.75 years) and 238 adults from general population (53.8% females; Mage = 31.75 years). The five factor model was evaluated with CFA and exploratory structural equation modeling (ESEM); non-substantive competitive models were also estimated. In addition, the empirical differentiation between factors was evaluated by comparing the squared root of the average variance extracted and the interfactorial correlation. The reliability was estimated by coefficients ω and H, and we analyzed the difference between ω and α. The results showed that the five factors structure were better represented by the ESEM, with empirically differentiated factors. The coefficients ω and H reached acceptable magnitudes and, in some cases, they differ from α.