Objective: Characterization of risk factors for ADHD in infancy may enable early intervention to diminish the symptoms that ensue. Method: In a retrospective study, the well-baby-care clinic records from birth to 18 months of age of 58 children diagnosed at school age for ADHD were compared with those of 58 control children, and the differences between the two groups were statistically analyzed. Results: Eight parameters during infancy were found to be significantly associated with later development of ADHD: at 0 to 1 month—advanced maternal age, lower maternal education, family history of ADHD, and social problems; at 3 and 18 months—decrease in head circumference percentile; at 9 and 18 months—delay in motor and language development, and difficult temperament. The predictive regression model accounted for 58% of the variance. Conclusion: This study highlights early risk markers in infants and toddlers that may predict the development of ADHD. (J. of Att. Dis. 2012; XX(X) 1-XX)