INTRODUCTION: Patients with acquired brain injury affecting the frontal cortex and individuals with substance use disorders share a range of behavioral problems, including apathy, poor self-control, and executive dysfunction. The Frontal Systems Behavioral Scale (FrSBe) is a self-report instrument designed to measure behavioral problems resulting from damage to the frontal–striatal neural systems, involved both in brain insult and addiction. The aim of this study was twofold: (1) to compare the scores from the Spanish version of the FrSBe with the norms collected for American, English-speaking population; and (2) to examine the ability of the FrSBe to discriminate between two clinical populations (acquired brain injury (ABI) and addiction) with putative frontal dysfunction, as compared to a group of healthy participants. PATIENTS AND METHODS: A total of 139 volunteers participated including 46 patients with frontal ABI (F-ABI), 57 abstinent substance abusers, and 36 healthy controls from the Spanish population. A Spanish version of the FrSBe was administered to all participants. We conducted multivariate analyses of variance to examine group differences across the three subscales: apathy, disinhibition, and executive dysfunction; and in the FrSBe total score. RESULTS: F-ABI and substance abusers had higher scores (i.e., greater impairment) than controls on the FrSBe total score; F-ABI patients scored significantly higher than substance abusers, and substance abusers significantly higher than controls. For specific subscales, F-ABI patients had higher scores than substance abusers and controls in the subscales of apathy, disinhibition and executive dysfunction, whereas substance abusers had greater executive dysfunction than controls. CONCLUSIONS: The Spanish version of the FrSBe is a useful instrument for the detection of behavioral problems associated with frontal systems dysfunction in two clinical samples of Spanish-speakers.