PurposeIn children and adolescents, preoperative planning for a semi-implantable bone conduction device (SIBCD) is crucial. The geometric changes of the new version of a common SIBCD should enable a higher rate of successful implantation due to its flatter actuator. Thus, this radioanatomic study compared the rate of successful implantation of both device versions at the traditional mastoidal localization and two alternative sites, retrosigmoidal, and parietal, and investigated parameters helping to estimate the feasibility.MethodsA retrospective analysis of 136 CT scans of 0 to 20-year-old patients, evaluation of demographic parameters, radioanatomy, and assessment of head diameter was conducted. The feasibility was investigated for certain age groups at three implantation sites. Prediction of feasible implantation by means of different parameters was calculated.ResultsA significant higher implantation rate was observed with the new device for all three sites and age groups. The age group of 6–8 years (n= 19) had most striking differences with a 58.1% rate of successful implantation with the new device without spacer (80% with spacer) at the mastoidal localization, whereas none with the old implant. Head diameter was identified as the most predictive parameter regarding all implantation sites (mastoidal:p= 0.030; retrosigmoidal:p= 0.006; parietal:p< 0.0001), age for the mastoidal (p< 0.0001) and retrosigmoidal (p< 0.0001), and gender for the parietal site (p= 0.001).ConclusionThe geometric changes of the actuator lead to a higher rate of successful implantation in all age-groups and all three localizations with reducing the requirement for spacers. Parameters age and head diameter might aid in estimating the rate of successful implantation in young patients and may be a novel tool to assist in the decision-making process for a SIBCD.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00405-022-07752-6.