Objective: ADHD is often associated with difficulties in planning and time management. In this study, the authors examined the hypothesis that these functional problems in ADHD reflect systematic biases in temporal orientation. Method: To test this hypothesis, adults with ADHD (n = 30) and healthy controls (n = 60) completed the Swedish version of the Zimbardo Time Perspective Inventory (S-ZTPI). Results: Although a majority of the ADHD participants were tested under stimulant medication, they showed significant differences in all the six subscales of the S-ZTPI. Logistic regression analysis, with age, education, depression, and response inhibition as covariates, showed that the Future Positive Scale was the primary predictor of ADHD status. Conclusion: These findings suggest that ADHD is associated with systematic biases in habitual time orientation and that these differences may contribute to functional problems in ADHD. (Contains 4 tables.)