Objective: Evidence regarding comedication among individuals with ADHD is lacking, especially in adults. This study investigated comedication and polypharmacy with ADHD medications in adults. Method: We identified adults dispensed with ADHD medications during 2013 in Sweden and matched them to controls. Logistic regression was used to calculate odds ratios (ORs) of receiving other medications. Results: Individuals receiving ADHD medications had higher risk of receiving any major classes of somatic medications (ORs ranged from 4.1, 95% confidence interval [CI] = [4.0, 4.3], to 7.4, 95% CI = [6.5, 8.5] across age groups). They were more likely to receive respiratory system, alimentary tract and metabolic system, and cardiovascular system medications. In addition, they had higher risk of receiving any other psychotropic medications. The proportion of polypharmacy with five or more medication classes increased from 10.1% to 60.4% from 18 to 64 years. Conclusion: Comedication was more common in adults receiving ADHD medications. Potential benefits and harms of comedication and polypharmacy require further research. (J. of Att. Dis. XXXX; XX[X] XX-XX).