Characterisation of film digitisers should be the first step when using them in the medical field: unfortunately, there is still no standard protocol to do so. This situation is particularly critical because the use of film digitisers is becoming a routine procedure in centres willing to set up PACS systems. The assessment of basic parameters such as the range and resolution of optical density, the spatial resolution and the noise level can be easily implemented and allows a check on the level of image degradation produced by film digitising. Simple methods are reported which could be included in quality assurance programmes of hospitals or centres using these systems.