In Québec (Canada), the American cancer-root (Conopholis americana [L.] Wallr.) is an obligate parasite that grows on the roots of red oak (Quercus rubra L.). Designated as vulnerable in the province, this plant is much rarer than its host and is restricted to a few south-facing rocky slopes. Following the discovery of a population of about 2,000 stems in the Rawdon area, 2 hypotheses were explored to try to explain the current known distribution of the species: 1) insufficient survey effort and 2) habitat quality. However, the results obtained did not clearly support either of these hypotheses. Random factors, such as dispersal by black bear and white-tailed deer, may be involved.