This study aims to enhance the understanding about consumer food leftover behavior in an out-of-home setting by applying a decomposed perspective on attitudes and empirical data on 307 guests in a university canteen. Based on 12 belief statements, three attitude dimensions are derived: (1) Environment, (2) Self-Interest and (3) Resources. Path analyses on their interrelation with general attitude, behavioral intention and observed leftover behavior indicates that the dimensions have distinctive behavioral effects. Moreover, these effects differentiate when portion sizes as a situational determinant of plate leftovers are introduced as grouping variable