Since drug related variability arises from different origins, particularly driven by the behaviour or physiology of the patient, the problems of drug intake and drug disposition are separately presented in general. To overcome the potential drawbacks of this artificial split, we propose in this paper a combined illustrative approach, named compliance spectrum, such that these two subprocesses can be equitably studied and visualized. We construct the compliance spectrum based on the Bayesian decision method we previously developed for the inverse problem of patient compliance within the framework of Population-PK. This spectrum provides an intuitive and interactive way to evaluate the relationship between drug intake and drug disposition along with their consequences on PK profile. As well, it opens a new direction for model quality diagnostic.