Background: Public attitudes towards persons with intellectual disabilities (IDs) have a significant effect on potential community integration. A better understanding of these can help target service provision and public awareness programmes. Objectives: The objective of the present study is threefold: (1) describe public attitudes towards persons with ID along affective, cognitive and behavioural dimensions; (2) compare and contrast attitudes according to sex, age, education and income, as well as frequency and quality of contacts with persons with ID; and (3) ascertain whether the level of functioning has an effect on attitudes. Methods: The "Attitudes Toward Intellectual Disability Questionnaire" (ATTID) was administered by phone to 1605 randomly selected adult men and women, stratified by region in the province of Quebec, Canada. The ATTID uses a multidimensional perspective of attitudes that reflect affective, cognitive and behavioural dimensions. Results: The results showed that public attitudes were generally positive regarding all three attitudinal dimensions. Public attitudes towards persons with ID are presented in terms of the five factors measured through the ATTID: (1) discomfort; (2) sensibility or tenderness; (3) knowledge of causes; (4) knowledge of capacity and rights; and (5) interaction. Attitude factor scores vary as a function of participant characteristics (sex, age, education and income) and the degree of knowledge about ID, the number of persons with ID known to the participants, as well as the frequency and quality of their contacts with these persons. Men had greater negative attitudes than women as regards the "discomfort" factor, while women had more negative attitudes regarding the "knowledge of capacity and rights" factor. More positive attitudes were revealed among younger and more educated participants. Attitudes were generally not associated with income. Public attitudes tended to be more negative towards people with lower functioning ID. Conclusion: These results yield useful information to target public awareness and education. (Contains 4 tables.)