The aim of the current study is to investigate the impact of counselling-based training on online peer support by comparing the interventions of trained peer supporters as opposed to non-trained peer supporters. Two independent raters analysed 746 support posts published during a period of one year at the "Student to Student" online peer support discussion forum at University of Athens. Results showed that the 30-hour counselling-based training used in this study allowed trained peer supporters to use basic counselling skills, such as open-ended and closed-ended questions and paraphrasing more often and even use relatively complex techniques, such as problem solving or definition of the main problem that non-trained supporters did not use at all or used very rarely. In addition, training did not seem to affect the peer support relationship, as indicated by the lack of differences between the two groups on empathy, acceptance and empowerment. Based on these findings, it was concluded that the training enhanced the peer support offered without compromising the nature of the relationship formed between peers. Therefore, brief counselling-based training can be an integral part of every peer-moderated online support programme.