The Personality Assessment Inventory (PAI; Morey, 1991, 2007) is among the most important personality and psychopathology assessment tools. However, its psychometric properties in the Spanish-speaking prison population have not yet been studied. We aimed to explore the factor structure of the Spanish adaptation of the PAI (Ortiz-Tallo et al., 2011) in an Ecuadorian sample of 811 convicted men using exploratory structural equation modeling, with the further objective of confirming its internal consistency. Hoelzle and Meyer (2009) identified three dimensions that are highly congruent across samples: general distress, elevated mood and dominance, and substance abuse and psychopathy. Taking these findings and the internalizing and externalizing dimensions (Ruiz & Edens, 2008) as a theoretical basis, three- and two-factor models were tested for the 22 scales and 11 clinical scales, respectively. We also tested four- and three-factor models that grouped the scales related to substance abuse as an independent factor, leaving intact the distribution presented by the remaining scales in the previous models. Although the original models showed a good fit, the 4- and 3-factor models obtained significantly better fit indexes. With respect to reliability, the Cronbach’s alpha coefficients ranged from .49 to .89. This version shows acceptable psychometric properties in correctional settings.The authors would like to thank the Health Coordination Zone 8 (Ministry of Public Health of Ecuador) for supporting and partially funding this study. In addition, this work was partially supported by the Regional Ministry of Economy, Innovation, and Science from Andalusian Government (Project: P2012-SEJ1723) and the Spanish Ministry of Economy and Competitiveness (Project: PSI2013-42792-R)