The aim of this study is to describe teenagers' experience of being diagnosed with cancer. A cancer diagnosis very dramaticaly changes the lives of a teenager and its relatives. Cancer is a loaded word that most people associate with death and the teenager and its relatives generally react with despair and anxiety towards. Adolescence is a very emotionally difficult period with many physical and psychological changes, and it is therefore particularly difficult to suffer from a serious illness like cancer during this period. The method used when conducting this study is qualitative content analysis of various blogs written by teenagers living with cancer and resulted in six categories. The result of this study shows that the analyzed teenagers have similar feelings and experiences, although they are described in various ways. Constant fear and living in uncertainty are considered to be particularly difficult. Teenagers who have cancer develope a different outlook on life and value small things differently. The teenagers included in this study have often felt alone in their situation and that no one understands them. Blogs have been used as a form of therapy where the teenagers can express their feelings. A nurse can inform and encourage patients to use blogs both in order to read about people in simular situations and also as a forum to express their own feelings.