The stomach has long been recognised as a depot for postmortem diffusion. A better understanding of the phenomena of postmortem diffusion would aid forensic practitioners in their interpretation of toxicological results. A limitation of previous stomach diffusion studies was the lack of ability to visualise postmortem diffusion in real time, the use of μX-ray Computed Tomography (CT) could overcome this problem. We utilised CT to track the diffusion of the contrast medium caesium ions (Cs+) (administered by oral gavage) from the rat stomach over 6 days. We investigated the influence of temperature (4 °C and 20 °C) and body position (horizontal and vertical). The results show that the a) diffusion of Cs+ from the stomach can be visualised over 6 days, over which a significant amount (∼50 %) of the diffusion occurs in the first 24 h following administration; b) storing the rat at 4 °C reduces the distance of diffusion from the stomach by ∼ 66%; c) body position influences the route of diffusion and d) in 2 of the 16 rats studied Cs+ was found in the right lobe of the liver. Overall these results show that CT using Cs+ is a good model to visualise postmortem diffusion and that bodies show significant variation in postmortem diffusion.It is also clear that bodies should be refrigerated and postmortem samples should be taken as soon as possible to minimise the influences of postmortem diffusion from the stomach.