Synthetic messenger RNA encapsulated in lipid nanoparticles (mRNA-LNP) is a transient gene delivery substrate which came to worldwide attention after its successful application for COVID-19 vaccines. Several publications have demonstrated that when delivered by the intravenous route, mRNA-LNPs accumulate in the liver and the encoded gene product is predominantly expressed by hepatocytes. However, relatively little is known about the effect of liver disease on mRNA-LNP uptake or expression, or the delivery of mRNA-LNPs to liver tumours. We set out to characterise the expression of mRNA-LNP-encoded reporter genes in mice with healthy and fibrotic livers, and in mouse models of primary and secondary liver cancer, using a variety of orthogonal biochemical and imaging techniques. We found that delivery of mRNA-LNPs is unaffected by mild chemical damage, but moderately impaired by severe fibrosis and cirrhosis. Delivery of mRNA-LNPs to liver tumours is comparable to the adjacent liver tissue in spontaneous hepatocellular carcinoma, xenografted hepatocellular carcinoma, and xenografts derived from lung and colorectal cancers. However, delivery of mRNA-LNPs to tumours located elsewhere in the body is weak to undetectable. Our results suggest that hepatic location, rather than cellular identity, is important for mRNA-LNP uptake into primary and secondary liver tumours. Our work demonstrates the range of possible outcomes after mRNA-LNP administration at both the whole-organ, whole-tumour and cellular scales, providing an important resource for investigators aiming to use mRNA-LNPs in hepatic biology research or as future treatments for liver disease and liver cancer.