[show abstract][hide abstract] ABSTRACT: Guided self-help via Internet is a promising way of treating panic disorder (PD). The present study examined the effects of a self-help program via Internet with weekly therapist contact for PD after disseminated to a new country. Predictors of outcome were also examined. The study was an open trial with 27 participants with PD with or without agoraphobia as their primary diagnose. Medium to large effects on PD-symptoms were reported after treatment and at 6months follow-up, with smaller effects on secondary outcome measures, i.e. depression, interpersonal problems, and sleep problem. The attrition rate of 30% in present study was higher than in Swedish studies. Predictor analysis showed that participants with longer duration of PD-symptoms had less improvement on all outcome measurers, whereas higher age predicted more improvement. The guided self-help program remained effective when disseminated to a new country, but the high attrition rate needs to be addressed in future studies.