For residents of territories along the Techa River that was contaminated with radioactive substances in the 1950s, bone-seeking beta-emitting 89,90Sr were the main source of internal exposure of active (red ) bone marrow (AM). The dose of these radionuclides conditions the severity of leukemia risk for them. Improvement of the methods of internal AM dosimetry is an important task. Computational 3D phantoms of the skeleton sites are a component of the solution for this task. Simulation of radiation transfer in a heterogeneous bone model allows estimating the dose conversion factors from radionuclide activity to AM dose. This manuscript continues the series of papers covering the development of a set of computational phantoms of a reference human being of different age. The objective of the study was to develop a computational phantom of a one-year-old child skeleton for internal AM dosimetry (exposure due to incorporated beta emitters). Using the original SPSD (stochastic parametric skeletal dosimetry) model, we develop voxel 3D models of skeletal sites. Skeleton sites with active hematopoiesis were modeled as a set of phantoms of simple geometries. Distribution of AM throughout the skeleton and parameters of the phantoms were assessed on the basis of the published results of measurement done in real bones of children aged 9 months to 2 years. The generated computational phantom of a one-year-old child consisted of 39 segments. It simulates the structure of the bone tissue, location of AM, and population variability of the skeleton microstructure and size parameters.