According to Information-Motivation-Behavioural Skills model (IMB), accurate Information, strong Motivation and adequate Behavioural skills are prerequisites of treatment adherence. This model has been verified among chronically ills patients, usually suffering from one particular disorder. No studies report how the model fits data from a more diverse group. The aim of the study was to analyze adherence and its barriers in a group of three hundred patients suffering from various, common chronic disorders. They filled out IMB and Adherence Questionnaire. Information and Motivation correlated moderately (.35). Behavioural Skills was the strongest predictor of adherence (.24). An additional relationship was found: Information and Motivation interacted and the role of either of these dimensions vanished if the indices of the other were high enough. The relationships between IMB dimensions and adherence were confirmed in a varied clinical sample. Behavioural skills must be considered when working with non-adherent patients, as they are the strongest predictor of adherence. Other interventions may be limited to either Information or Motivation only if there is a chance of raising one of them to extreme levels. This may be useful with special cases, when increasing both is problematic.