Background. Malnutrition and delayed growth are commonly seen in children with cystic fibrosis and are indicators of poor prognosis. Understanding the factors that affect growth and nutritional status may improve care, treatment and longevity. Objectives. To determine how nutritional status, as estimated using anthropometric measurements, in children with cystic fibrosis is affected by 1) the type of CFTR mutation, 2) colonization by Pseudomonas aeruginosa, and 3) age at diagnosis. The relationship between nutritional status and pulmonary function was also investigated. Material and Methods. Anthropometric data on height, weight, circumferences and skinfold thicknesses were extracted from the medical histories of 41 boys and 48 girls diagnosed with cystic fibrosis who were treated at the Institute of Mother and Child in Warsaw, Poland. Muscle and fat tissue area were calculated from these measurements. The values for children with CF were compared to the Polish national growth reference charts. Multivariate linear regression tested the effect of three factors on nutritional status: colonization with P. aeruginosa, age at diagnosis, and the type of CFTR mutation. Results. All values for children with CF were significantly lower than in the reference population. The results show that, in the children examined, nutritional status is more adversely affected than growth. Of the factors related to the clinical picture of the disease, only the presence of respiratory tract colonization by P. aeruginosa had an effect on physical development in the children examined. Neither the type of mutation present nor age at diagnosis had any significant effect. Conclusions. Chronic colonization by P. aeruginosa interfered with growth and markedly worsened nutritional status, and was also associated with reductions in both total and lean body mass. Early nutritional intervention can improve nutritional state and pulmonary function in children with CF (Adv Clin Exp Med 2014, 23, 5, 775-783).