Objective: To determine the lost productivity of Canadian patients with moderate to severe psoriasis. Methods: Seventy-nine consecutive Canadian dermatology patients were interviewed and completed the Work Productivity and Activity Impairment Questionnaire. The inclusion criteria were diagnosis with moderate to severe psoriasis by the treating dermatologist; 19 year of age or older and currently receiving treatment for psoriasis with either a biologic or alternative therapy such as phototherapy, systemic or topical treatments. Patient interviews and data collection occurred between September 21st, 2005 and November 8th, 2005. Results: Eighty-one percent of patients reported working full-time. On average, 2.6 hours (± 6.8)(about 6% of total work hours) were lost from work per week due to psoriasis-related events. When asked how much psoriasis affected their productivity while working, individuals on average reported approximately 20% impairment in productivity due to psoriasis. Twenty-six percent of the patients indicated psoriasis was the reason for altering their job type, description, or work responsibilities. Thirty-four percent of patients believed that their condition affected their choice of career or ability to find a job. Assuming patients were not paid during their absenteeism, absence from work resulted in lost mean patient wages of CDN$2580.97 per person per year. With an estimated 330,000 Canadians suffering from moderate to severe psoriasis, total lost wages due to moderate to severe psoriasis may cost up to approximately CDN$852 million for all moderate to severe psoriasis patients in Canada. Conclusion: The results of this study indicate that moderate to severe psoriasis may have a substantial impact on the work productivity of patients with this disease. Further studies on lost productivity as well as societal impact of moderate to severe psoriasis are needed.