There is a growing interest in the objective assessment of health related outcomes using technology providing quality measurements to be applied not only in daily clinical practice, but also in scientific research. Differences in the understandings of the condition and the terminology used between people with Parkinson's (PwPs), clinicians and technical developers may influence the progress of a participatory design process. This paper reports on a participatory design process to achieve a consensus among PwPs, clinicians and technologists over the selection of a set of symptomatic domains to be continuously assessed, in order to provide results relevant to both PwPs and clinicians. The methods used were a Web based user survey, end-user focus groups, ranking by combined methods, a Delphi process performed among clinicians and scientists, and prioritization of the results in a concertation workshop for PwPs, clinicians and technologists. The following symptomatic domains were commonly agreed by PwPs and clinicians to be of central importance in a system of continuous assessment: hypokinesia/bradykinesia, tremor, sway, gait, sleep and cognition. This list satisfied both the needs of the PwPs and the concerns of the clinicians regarding the means of advancing new strategies in assessment and interventions in PD. A participatory design strategy allowed the definition of a consensual list of symptomatic domains. Both the strategy and the achieved results may be of relevance for similar interdisciplinary approaches in the field of PD using a participatory design involving patients, clinicians and technologists.