Background. Tissue diagnosis is mandatory prior to treatment of an abdominal or pelvic lesion in a child. Objectives. To compare the diagnostic yield and complications of fine-needle aspiration biopsy (FNAB) and 1.2-mm needle core biopsy (NCB) for abdominal and pelvic lesions in children using US guidance. Material and methods. Ninety consecutive abdominal or pelvic US-guided biopsies in 61 children; 53 FNAB procedures in 43 children and 37 NCB procedures in 34 children were retrospectively analysed. Fifty-seven biopsies were performed on malignant lesions and 33 on benign lesions. In 15 children, both FNAB and NCB were performed at the same occasion. Results. FNAB was diagnostic in 41 (77 %) of 53 biopsies while NCB provided a correct diagnosis in 35 (95 %) of 37 biopsies. Results were similar in both malignant and benign conditions. Clinically important bleeding complicated three biopsies (3.3 %); in two after FNAB and in one after combined FNAB and NCB. Conclusion. If FNAB were to be replaced with 1.2-mm NCB using an automatic gun, the diagnostic yield for abdominal and pelvic focal lesions in children would improve significantly (P < 0.05) while the complication rate would remain low. NCB may reduce the need for diagnostic and staging surgery and repeated procedures.