Objectives. To measure the subjective sleep quality of prisoners complaining of insomnia and to compare it to the subjective sleep quality of prisoners who report "good sleep", in order to determine factors that predict insomnia and severity of insomnia. Participants and methods. PSQI and GHQ scores and patient history were obtained for 86 randomly chosen remanded prisoners complaining of insomnia and 61 randomly chosen prisoners who did not complain of insomnia. Results. PSQI total and component scores were significantly different between insomniac and not insomniac prisoners, except for C7 (daytime dysfunction). A history of sleeping problems before prison (odds ratio: 13.3), the subjective experience of having had stressful events during the past week (odds ratio: 8.5), being separated or divorced (odds ratio: 8.8), GHQ >10 (odds ratio: 8.8), a history of psychiatric problems (odds ratio: 8.3) and the consumption of opiates (odds ratio: 7.9), and to a lesser degree “no sports in prison” and stress related to judicial, familial and prison problems, were predictors of insomnia. We did not find any evidence in this study that work or consumption of caffeine in prison were factors that distinguished good sleepers from insomnia patients. Conclusions. Our study helps prison physicians to identify prisoners at risk for insomnia and to obtain some orientation for treatment decisions. Psychological support to reduce context related stress should be routinely offered to insomniac prisoners.