Objective Chinese hamster ovary (CHO) cells are the leading cell factories for producing recombinant proteins in the biopharmaceutical industry. In this regard, constraint-based metabolic models are useful platforms to perform computational analysis of cell metabolism. These models need to be regularly updated in order to include the latest biochemical data of the cells, and to increase their predictive power. Here, we provide an update toiCHO1766, the metabolic model of CHO cells. Results We expanded the existing model of Chinese hamster metabolism with the help of four gap-filling approaches, leading to the addition of 773 new reactions and 335 new genes. We incorporated these into an updated genome-scale metabolic network model of CHO cells, namediCHO2101. In this updated model, the number of reactions and pathways capable of carrying flux is substantially increased. Conclusions The present CHO model is an important step towards more complete metabolic models of CHO cells.