BACKGROUND: Neuroblastoma is a highly lethal malignancy of young children. Mesenchymal stromal cells (MSCs) may represent a novel cellular delivery vehicle due to their innate tumor-homing properties. We compared in vivo homing abilities of placental-derived MSCs (PMSCs) and bone marrow-derived MSCs (BM-MSCs) in an orthotopic neuroblastoma xenograft. METHODS: 28 mice underwent direct implantation of neuroblastoma cells (cell line NB1643) into the adrenal gland followed by intraperitoneal injection of 5 × 10(6) MSCs (PMSC n = 13, BM-MSC n = 13, PBS controls n = 2). MSC migration was monitored with in vivo imaging system (IVIS) radiance measurements at multiple timepoints post-MSC injection. Necropsy timepoints were 72 h (n = 10) and 7 days (n = 16). Ex vivo imaging was performed on all adrenal masses and select organ tissues. Immunohistochemistry (IHC) assessed the presence of MSCs in tumors. RESULTS: IVIS demonstrated initial diffuse signal that migrated to the left abdomen. Radiance decreased over time, but MSC signal persisted at day 7 in all animals. Ex vivo IVIS demonstrated signal in the adrenal tumor but not other organs. There was no significant difference in average ex vivo adrenal mass radiance between MSC groups (p = 0.74). IHC confirmed presence of both MSC types within the tumor. CONCLUSION: PMSCs and BM-MSCs successfully migrated to neuroblastoma tumor tissues in vivo without evidence of migration to other organs. MSCs migrate within 72 h and persisted within the tumor up to 7 days. There was no significant difference in homing capabilities of PMSCs compared to BM-MSCs, indicating that either cell type has potential as a drug delivery vehicle. TYPE OF STUDY: Original Research. LEVEL OF EVIDENCE: n/a.