Purpose Spinal lipoma of the filum terminale (LFT) is a congenital lumbosacral anomaly that can cause tethered cord syndrome. Purposes of this study are to clarify preoperative characteristics of LFT, to elucidate surgical effects, and to discuss the rationale of prophylactic surgery for LFT. Methods Medical data of 174 children (2008–2014) who underwent section of LFT were prospectively recorded for prevalence of symptoms, skin stigmas, and associated malformations, motivator of diagnosis, conus level, and surgical outcome. Mean age at surgery was 4.1 ± 4.2 years (37 days to 17.7 years). Results Ninety-four children (54.0 %) had skin stigmas and 60 (34.5 %) had certain perineal malformations. Seventy-nine children (45.4 %) were symptomatic. The most common motivator for diagnosis was skin stigmas (44.3 %), followed by associated malformations (33.3 %), and symptoms (20.1 %). The age at surgery was significantly older in symptomatic patients than in asymptomatic patients ( p  < 0.001). Surgery improved symptoms in 50 % of patients at 2.1-year follow-up period. Of 85 asymptomatic patients, all except one remained asymptomatic postoperatively and none of the symptomatic patients deteriorated. The presence of associated malformations and the conus level did not affect surgical outcome. Postoperative complications developed in nine patients (5.2 %): seven transient local problems, one definitive urological deterioration, and one transient respiratory problem. Conclusions Surgery for LFT was a simple and safe procedure. It improved half of symptomatic patients and stopped the deterioration of the others. Even if only one of the asymptomatic patients deteriorated at maximum follow-up, the role of prophylactic surgery remains a point of discussion.