The management of dog behavioural problems requires the expertise of professionals such as the veterinary behaviourist. Clinical assessment of behavioural disorders allows the veterinary behaviourist to formulate a diagnosis and prescribe a behavioural and/or pharmacological therapy. The objective of such therapy is to produce a stable change in the perception of a stimulus and the resulting emotion, leading to the correction of the behavioural problem. It may be crucial to evaluate the subject's pathological state in response to the observed symptoms in order to identify the functional impairment of the pivotal neurotransmitter systems involved in the disorder. This allows selecting a suitable pharmacological treatment. In order to implement behavioural therapy, the veterinary behaviourist collaborates, where necessary, with a team of qualified canine trainers.