The aim of this study was to gain knowledge about the specific needs that a web-based support system for young carers (YCs) must meet. Twelve young people with experience of caring for and supporting a close friend, partner or relative with mental illness (MI) were interviewed about their life situation, support needs and opinions about a hypothetical web-based support system. The transcribed interviews were analysed using content analysis. The analysed data were organised into three themes relating to support needs, each including a number of sub-themes: knowledge--understanding MI, managing the mentally ill person and self-care; communication--shared experiences, advice and feedback, and befriending; and outside involvement--acute relief, structured help and health care commitments. Web-based support for YCs may be a suitable way to meet the need for knowledge and to meet some of the needs for communication. We have outlined a concept of a geographically anchored web support to meet the need for befriending, facilitate connections to health and social care, and increase understanding and interaction between the parties involved. Further research is needed to corroborate the results.