Molecules with identical chemical, but different isotopic composition, are known as isotopologues. Several isotopologues of H2O present in the Earth's atmosphere can be retrieved with the satellite instrument ACE-FTS on SCISAT. In this talk, I will describe my intercomparison work on water isotopologues with a heavy oxygen atom (Oxygen-17 and Oxygen-18). The main part of this study is a comparison with the satellite instrument SMR on Odin.