Extensive peatlands in Indonesia are a major store of carbon. Deforestation, conversion to other land uses, especially plantations of oil palm and pulpwood trees, and recurrent fires have recently caused the release of large amounts of this carbon to the atmosphere. If these large emissions from degrading peatlands are taken into account Indonesia is one of the largest emitters of CO2 worldwide. To improve estimates of the amount of carbon stored in Indonesian peatlands we applied 3D modelling based on the combined analysis of satellite imagery (Landsat ETM+, SRTM) and 750 in situ peat thickness measurements. We demonstrate that SRTM radar data can be used to determine the extent and topography of the dome shaped surface of a selection of peatlands in Central Kalimantan, South Sumatra and West Papua. A strong correlation was obtained between the convex peat dome surface and the underlying mineral ground, which was used to calculate the peat volume and carbon store. Conservatively, we estimate that at least 55 ± 10 Gt of carbon are stored in Indonesia's peatlands. This amount is higher than previous results published because it takes into account the biconvex nature of the tropical peatlands. With this huge carbon storage and the current rate of degradation the tropical peatlands of Indonesia have the power to negatively influence the global climate. © 2008 Elsevier B.V. All rights reserved.