For individuals with autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD) work participation is a challenge, as shown by their low employment rates. The aim of this study was to investigate which factors predict work participation, finding work as well as maintaining employment, of young adults with ASD as well as ADD. We obtained data on 563 individuals with ASD and/or ADD, aged 15-27 years. The follow-up period ranged from 1.25 to 2.75 years. Being male (for ADD), living independently (for ASD), expecting to be able to work fulltime (for ASD and ADD), high perceived support from parents and perceived positive attitude of parents regarding work (for ASD and ADD) and perceived positive attitude of social environment (for ADD) predicted finding work by the young adult, while being male (for ADD) and higher age (for ASD and ADD) and positive attitude of social environment regarding work (for ASD) predicted maintaining employment. Both personal and social factors predict work outcome and should be taken into account when supporting individuals with DD in their transition to work.