This paper revisits some aspects of carbon-11 radiochemistry from the production of the primary labeling reagents and fast chemical transformations used to convert them into more useful building blocks such as [11C]methyl iodide and [11C]carbon monoxide. The application facet covers traditional methylation, carboxylation and other reactions in the preparation of PET tracers. Technical aspects and strategies in handling labeling syntheses are also included. Distinct attention is then given to methods for the 11C-labelling of carbamide and carbamate functional groups at the carbonyl position, considering the wide choice of protocols and starting materials that have become available for this purpose. Concluding sections provide an overview of contemporary practices for the purification of labeled compounds and preventing their radiolytic decomposition.