The purpose of this paper is to clarify the distribution of benign vs malignant pulmonary nodules which are seen on spiral CT in children with malignant extra-thoracic solid tumors. Seventy-four children with known solid, extra-thoracic tumors underwent spiral CT of the chest. According to the initial and follow-up (interval 9.2+/-4.7 months) findings, the children were graded into four groups: I = normal; II = solitary nodule unchanged at follow-up; III = multiple nodules with one or more than one unchanged at follow-up; and IV = solitary or multiple nodules all changed at follow-up. Nodules without change at follow-up were regarded as benign. Forty-nine children did present with normal pulmonary CT exams. In 7 cases solitary pulmonary nodules were found unchanged (group II) at follow-up and in 2 cases (group III) some of the nodules were stationary. Thus, 12% (9 of 74) presented with at least one pulmonary nodule that did not change at follow-up. Solitary nodules (in groups II and IV) with a diameter <5 mm were in 70 % (7 of 10) unchanged at follow-up and regarded as benign. In children with known solid extra-thoracic tumors at initial presentation, 70% of solitary nodules ( <5 mm) may be benign. To avoid overstaging, smaller solitary nodules must not automatically be regarded as metastases.