We evaluated the rate and type of second malignant neoplasms (SMN) after BFM treatment of children with Non-Hodgkin lymphoma (NHL). Between January 1981 and February 2003 2451 patients (pts) <15 years (y) of age at diagnosis were enrolled into the subsequent trials NHL-BFM 81, 83, 86, 90, and 95. Pts with lymphoblastic lymphoma (LBL) (n=547) or non-anaplastic peripheral T-cell lymphoma (n=97) received acute lymphoblastic leukemia (ALL)-type therapy including cumulative doses of cyclophosphamide (max. 3g/m2), daunorubicine/doxorubicin (max. 280mg/m2), but, except few pts, no etoposide. Prophylactic cranial radiotherapy (CRT) was given in stage III/IV (omitted in NHL-BFM95). Pts with mature B-cell neoplasms (n=1597), or anaplastic large cell lymphoma (n=210) received B-type therapy, consisting of 2–8, 5-day courses including cumulative doses of cyclophosphamide (max. 7g/m2), ifosfamide (max. 8g/m2), doxorubicine max. 150mg/m2 (in trial 81 max. 200mg/m2), and etoposide (max. 1.4g/m2). CRT was omitted since trial NHL-BFM86. With a median follow-up of 6.9 (range 0.2–22.6) years the probability of survival at 15 y was 83+1%. By June 2005, 47 SMN were documented, including 16 acute myeloid leukemias/myelodysplastic syndromes (AML/MDS), 11 NHL, 2 ALL, 1 Hodgkin's lymphoma, 7 brain tumors, and 10 other SMN. All SMN occurred in first remission after a median time of 2.9 (range: 0.4–12.3) years from diagnosis of NHL. The cumulative incidence of SMN at 15 y was 4.0% (95% confidence interval [CI]: 1.9%–6.1%) for the total group. The cumulative incidence of SMN was significantly higher among pts with LBL receiving ALL-type therapy (6.3% at 15 y [95%CI: 2.4%–10.3%] (13 AML/MDS, 2 NHL, 3 brain tumors, and 3 other SMN), as compared to pts with other NHL-entities receiving B-type therapy (3.4% at 15 y [95% CI: 0.5–6.4%] (3 AML/MDS, 9 NHL, 2 ALL, 1 Hodgkin's lymphoma, 4 brain tumors, and 7 other SMN), p=0.002. There was no significant difference of cumulative incidence of SMN in pts who received CRT compared to pts not receiving CRT. However, 5 of 7 pts, who developed brain tumor, received CRT of 12–24 Gy. Also, there was no significant correlation between the incidence of SMN and the cumulative doses of drugs, except for anthracyclines. For pts receiving a cumulative dose of anthracyclines of >160mg/m2 (almost exclusively pts with LBL receiving ALL-type therapy) the cumulative risk for SMN at 15 y was 6.5% (95% CI: 1.5-11.5%), as compared to 2.0% (95% CI: 1.1–2.9%) for pts with lower doses, p=0.007. Exposure to etoposide was not a risk factor for secondary AML/MDS (11 of 16 pts with sec. AML/MDS did not receive etoposide). In a Cox regression analysis only diagnosis of LBL remained a significant risk factor for SMN (RR 2.5, 95% CI 1.4–4.4). Our analysis revealed a cumulative risk for SMN of 4% at 15 y after successful treatment of childhood NHL. The cumulative incidence of SMN was significantly higher in LBL-pts than in other pts. AML/MDS were the most frequent SMN following LBL while second lymphoid malignancies were the most frequent SMN following non-LBL.