Background Collaboration between general practice and mental health care has been recognised as necessary to provide good quality healthcare services to people with mental health problems. Several studies indicate that collaboration often is poor, with the result that patient' needs for coordinated services are not sufficiently met, and that resources are inefficiently used. An increasing number of mental health care workers should improve mental health services, but may complicate collaboration and coordination between mental health workers and other professionals in the treatment chain. The aim of this qualitative study is to investigate strengths and weaknesses in today's collaboration, and to suggest improvements in the interaction between General Practitioners (GPs) and specialised mental health service. Methods This paper presents a qualitative focus group study with data drawn from six groups and eight group sessions with 28 health professionals (10 GPs, 12 nurses, and 6 physicians doing post-doctoral training in psychiatry), all working in the same region and assumed to make professional contact with each other. Results GPs and mental health professionals shared each others expressions of strengths, weaknesses and suggestions for improvement in today's collaboration. Strengths in today's collaboration were related to common consultations between GPs and mental health professionals, and when GPs were able to receive advice about diagnostic treatment dilemmas. Weaknesses were related to the GPs' possibility to meet mental health professionals, and lack of mutual knowledge in mental health services. The results describe experiences and importance of interpersonal knowledge, mutual accessibility and familiarity with existing systems and resources. There is an agreement between GPs and mental health professionals that services will improve with shared knowledge about patients through systematic collaborative services, direct cell-phone lines to mental health professionals and allocated times for telephone consultation. Conclusions GPs and mental health professionals experience collaboration as important. GPs are the gate-keepers to specialised health care, and lack of collaboration seems to create problems for GPs, mental health professionals, and for the patients. Suggestions for improvement included identification of situations that could increase mutual knowledge, and make it easier for GPs to reach the right mental health care professional when needed.