The aim of the present study was to conduct the preliminary adaptation of the Morningness-Eveningness-Stability-Scale improved (MESSi) to Spanish population, testing its factor structure and construct validity. Participants were 261 adults (65% women; M = 31.4, SD = 12.01) who filled out measures of Morningness-Eveningness (MESSi and CSM), sleep habits, personality traits, positive and negative affect, and subjective level of alertness during the day. Psychometric results supported a three

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... rial model with the factors Morning Affect, Eveningness and Distinctness (RMSEA = .072). The factors showed good internal consistence (α = 0.72–0.85). The pattern of correlations between MESSi and the other measures were in the expected direction (low to moderated size effects). Morning Affect was positively predicted by morning chronotype (R 2 = .64), Eveningness was negatively predicted by age and positively by evening chronotype (R 2 = .41), and Distinctness was negatively predicted by sex (women reported higher DI than men) and age (R 2 = .08). This study provides evidence for the factor structure of a new measure of Morningness-Eveningness based on a rigorous psychometric evaluation.