Health resource use and identification of related costs are two essential steps in health economics assessment. The elicited costs will be balanced with health outcome improvement and enable the comparison of different diagnostic procedures or therapeutic strategies from a health economic point of view. The cost typology can be disentangled in three main components, that is, direct cost related to health resource use, indirect costs related to productivity loss and sometimes intangible costs (costs related to pain and suffering). These costs can be elicited from different perspectives depending on the general aim of the assessment: payer, societal perspective or patient perspective. Practically, the first step corresponds to the quantification of health resource use, that is, number of consultations, biological or imaging workups, hospitalisation, dispensed medication units or days on sick leave. It can be done by specific self-questionnaires or by access to insurance health databases. The second step is then to value each health resource use item, based on available public databases—either produced by insurance entities or statistics institute—providing the unit costs for each item. Importantly, substantial variability does exist in the costing exercise, requiring accepting a certain uncertainty around cost estimates. This can be taken into account by sensitivity analyses, which capture in what extent measurement error can impact cost assessment, depending on different hypotheses or assumptions. One essential element of health economic assessment is the identification of costs incurred by or associated with a specific health condition for a study on the economic burden of a disease—cost-of-illness study—or with a given diagnostic or therapeutic intervention in the context of health technology assessment in which these costs are compared with the alternative reference strategy—cost-effectiveness study.