This case report offers a different perspective on a patient with a long-term non-psychotic psychiatric disorder that was difficult to specify. The patient, a man in his 50s, was unable to profit from outpatient treatment and became increasingly dependent on mental healthcare – which could not be understood based on his history and psychiatric symptoms alone. By separating symptoms from illness behaviour, the negative course of this patient's treatment is analysed. Focusing on ineffective chronic illness behaviour by the patient, and mutual ineffective treatment behaviour by the clinicians, it becomes clear that basic requirements of effective treatment were unmet. By making a proper diagnosis, clarifying expectations and offering a suitable therapy, ineffective illness behaviour was diminished and this ‘difficult’ case became much easier for both patient and clinicians. The illness behaviour framework offers a useful, systematic tool to analyse difficulties between patients and clinicians beyond psychiatric symptoms or explanations.