OBJECTIVES Psoriasis is a chronic debilitating immune-mediated inflammatory disease, with no cure, affecting an estimated one million Canadians. Studies show that up to 85% of psoriasis is of plaque type and up to 25% of sufferers have either moderate or severe disease. There are no reliable estimates of the economic burden of psoriasis in Canada. The objective is to estimate the economic burden of moderate to severe chronic plaque psoriasis in Canada in 2008, inclusive of direct medical and non-medical, and lost productivity costs. METHODS Using a cross-sectional design, data were collected on 90 patients diagnosed with moderate or severe chronic plaque psoriasis in three dermatology clinics (British Columbia, Ontario, and Quebec). Data were obtained from three sources: clinic charts determining medical resources utilized for treatment; patient questionnaires eliciting information on non-medical resources utilized, lost productivity, and the impact on quality of life (QoL) using the Dermatology Quality of Life Index (DLQI); and unit costs (all in CDN$2008) from published sources. RESULTS The estimated mean annual costs of treating patients with moderate to severe chronic plaque psoriasis was $7966/patient, of which $4524 (95% confidence interval (CI): $2246 to $6802) was due to direct medical and non-medical costs, and $3442 (95% CI: $1293 to $5590) was due to lost productivity. The estimated mean DLQI of 6.7 is reflective of a moderate impact on QoL in moderate to severe psoriasis patients. CONCLUSIONS Extrapolating these costs to the estimated number of affected Canadians means that moderate to severe psoriasis costs on the order of $961.3 million (95% CI: $477.3 million to $1.4 billion) in direct medical and non-medical costs annually. The total cost to society is approximately $1.7 billion (95% CI: $752.0 million to $2.6 billion). This economic burden coupled with the QoL effect indicates the need for more efficient and long-term control.