This paper reviews the knowledge gap regarding the contributions of the clinical nurse specialist (CNS) in Canada. As a first step to deal with this gap, we address how the CNS role has been conceptualized and studied in Canada. Because the CNS is a clinical leader with a primary focus on improving the quality of nursing and patient care, we propose the Spheres of Influence Model for studying the contributions of the CNS. This model directs attention to various research questions, which are illustrated with sample questions for each of the spheres of influence: the patient/client sphere, the nurses/nursing sphere and the organizations/health systems sphere. Examining the role through these spheres of influence may be a better way to illuminate the contributions of the CNS to health services and to the provision of excellent nursing care.