The millions of ponds and small lakes in Arctic lowlands have been identified as biogeochemical hotspots with high process rates. However, water bodies with surface areas smaller than 1 km² are not captured on a global scale. This study upscales local, high-resolution water body size distributions to the regional scale in the Lena Delta (Siberia) and the Mackenzie Delta (Canada). We investigate (i) the variability of water body size distributions within and between the two deltas, and (ii) relate differences to hydrological, geomorphological and permafrost processes. Water bodies are mapped from aerial, TerraSAR-X and Kompsat-2 imagery with resolutions of 4 m and better. The Lena Delta features about 40% more ponds than the Mackenzie Delta. Within-landscape variability is low in both deltas which allows the estimation of regional distributions. Statistical properties of such regional distributions can be used to incorporate ponds and small lakes into larger-scale climate and ecosystem models.