Objective: Mixed-handedness among children has recently been proposed as a marker of neurodevelopmental disorder and ADHD. This study expanded this initial evidence to the questions of whether mixed-handedness as well as mixed-footedness are similarly associated with ADHD among adults. Method: Self-reported ADHD symptoms, handedness, footedness, and current depression and anxiety were assessed in a large, heterogeneous general population sample (N = 2,592). Latent variable analysis was used to investigate the structure and measurement properties of ADHD symptoms, the dimensionality of footedness, and the classification of lateral preferences. Results: Mixed-footedness was associated with probable ADHD (odds ratio [OR] = 1.76 [1.07, 2.89], p = .026). Left- and mixed-footedness were associated with higher inattention and impulsivity scores. Conclusion: Developmental continuities of the associations of mixed lateral preferences with ADHD from child to adult age seem to exist. In particular, mixed-footedness, rather than mixed-handedness, appears to be an ADHD marker among adults.