The invention relates to a device for assistance in the selection of a compression orthesis and in adapting same to the morphology of a limb. The inventive device consists of: means (26) for establishing a first file containing data representative of the morphological characteristics of the limb (30), comprising the three-dimensional co-ordinates of a mesh of points (68) with different heights; means (10) for establishing a second file containing data representative of the dimensional and rheological characteristics of the orthesis, which are defined with different heights; compression simulation means (48) which, using the data from the first and second files, can determine the compression pressure values that are likely to be exerted by the orthesis on the limb at a plurality of points of said mesh; and means (50) for displaying the pressure values thus determined in a graphical manner, for example, by overlaying a 3D graphical representation of the limb, or a section of same, with the false color- or grey level-coded calculated pressure.