To know more about the emotional well-being of women held in prisons in Spain by analyzing the state of mental health they present and investigating the factors that affect them.A sample of 434 inmates in Spanish penitentiary centers was studied. An ad hoc designed questionnaire was used and a logistic regression analysis was conducted to determine the variables and to what extent they influence emotional well-being.The existence of a statistically significant relationship between the well-being stages and the origin variables (region of origin of the women) and the history of substance addiction were confirmed. No significant relationship has been found for well-being levels from other variables (maternity, social or family support, gender violence or having or not having a partner).Having a problematic history of drug use negatively affects the levels of emotional well-being of women detained in prisons. The low levels of substance use in women of Latin American origin is related to their more positive levels of emotional well-being.