Thanks to Odin's frequency coverage, it was also possible to detect the H218O 548 GHz line, first in comet 153P/Ikeyax2013;Zhang in April 2002 [Lecacheux, A., Biver, N., Crovisier, J. et al., 2003, Observations of water in comets with Odin. Astron. Astrophys. 402, L55x2013;L58.] and then in comets C/2002 T7 (LINEAR), C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz). The 16O/18O isotopic ratio (≈450) is consistent with the terrestrial value. Ammonia has been searched for in three comets through its baf290ddae381da2457a2604"" title=""Click to view the MathML source"">JK=10x2013;00 line at 572 GHz and was tentatively detected in C/2001 Q4 and C/2002 T7. The derived abundances of NH3 relative to water are 0.5 % and 0.3 % , respectively, similar to values obtained in other comets with different techniques.