OBJECTIVE: The objective of the present study is to examine bereaved siblings’ perception of research participation. METHODS: A Swedish nationwide study on avoidable and modifiable health care-related factors in paediatric oncology among bereaved siblings who lost a brother or sister to cancer between the years 2000 and 2007 was conducted. Data are presented as proportions, and the differences between groups were statistically tested at the 5% significant level using Fisher’s exact test. RESULTS: Out of 240 eligible siblings, 174 responded (73 %). None of the siblings (0/168) thought their participation would affect them negatively in the long term. However, 13% (21/168) stated it was a negative experience to fill out the questionnaire, whereas 84% (142/169) found it to be a positive experience. Women were more likely to report their participation as positive in a long-term perspective compared with men (p = 0.018). CONCLUSIONS: None of the bereaved siblings in this Swedish nationwide study anticipated any long-term negative effect from their research participation. A majority reported it as positive to revisit their needs and experiences throughout their brother or sister’s illness and death 2-9 years following the loss. We believe that the stepwise approach used in this study contributed to the high acceptance.