Pre-sleep cognitive activity has been implicated in the maintenance of sleep-onset insomnia. The present study aimed to investigate the focus of attention, content and characteristics of cognition during the pre-sleep period. A semi-structured clinician-administered interview designed to index the content of pre-sleep cognition was completed by individuals diagnosed with sleep-onset insomnia (N = 30) and good sleepers (N = 30). The pre-sleep cognitive activity of insomniacs could be distinguished from that of good sleepers by being more focused on worries, problems and noises in the environment, and less focused on 'nothing in particular'. In terms of content, the insomnia group were more likely to think about not sleeping or about something that had happened during the day. Insomniacs experienced their pre-sleep cognitive activity as more occupying, less intentional, for a longer duration, and as causing more difficulty with sleep onset compared to good sleepers. Pre-sleep imagery was reported at similar rates across diagnosis, but was more distressing and more likely to be associated with strong physical sensations for the insomniac group compared with the good sleeper group. The present study provides a comprehensive investigation of pre-sleep cognitive activity and raises a number of areas for future research including monitoring of bodily sensations, imagery, problem-solving and non-active strategies in facilitating sleep onset.