Chronic disease has a psychological impact on the sufferer; however, it also affects the close ones. Its specific characteristics, course, and ambiguous prognosis lead to a change in situation in which the family was functioning before. In consequence, the disease affects dramatically the parents and the siblings of the ill person. The article is an attempt to assess the life quality of the siblings of cystic fibrosis’ sufferers. The total number of participants was 124. Four equal experimental groups were created - children with a sibling affected by the disease, parents of the affected child, and also control groups (children with healthy siblings and parents of healthy children). Each group consisted of 31 participants. In order to assess life quality, a polish version of KIDSCREEN-52 was employed. The results suggest that the siblings of people suffering from cystic fibrosis do not declare a lower life quality compared to children who have healthy siblings. Also, no significant differences in the assessment of life quality of healthy children were observed (when assessed both by the children themselves and by their parents).