BACKGROUND: Deletion of the long (q) arm of chromosome 18 causes a rare genetic disease termed 18q- syndrome. This syndrome has varying clinical presentation, depending on the extent of the deletion and the percentage of cells with abnormal chromosomes. One of the most common disorders in children affected by the disease is short stature, usually associated with growth hormone deficiency. Numerous reports on patients with 18q- syndrome show growth hormone treatment has significant therapeutic benefits, not only in terms of final body height but also cognitive functions and psychosocial development. CASE PRESENTATION: Here we describe the case of a 10-year-old girl with 18q- syndrome treated with recombinant human growth hormone from the age of 2. This is the first report of such a patient in Poland. After 8 years of observation, the child showed a clear benefit from recombinant human growth hormone treatment in terms of height and possibly mental development. The girl remains under cardiac care due to congenital heart disease and under neurological care for epilepsy. CONCLUSIONS: This case indicates the need for early diagnosis and multidisciplinary action to achieve satisfactory quality of life in patients with 18q- syndrome.