We explore the differences between mainstream and heterodox economists based on the responses to a questionnaire from a representative sample of Italian economists. Using different definitions for mainstream and heterodox economics, we compare the individual and academic characteristics of the economists belonging to these groups. We measure the within and between disagreement for each group and we test whether belonging to one or the other group predicts differences in economists' opinions on economic policy. Results show that: 1) mainstream and heterodox economists differ as to individual and academic characteristics and political views; 2) the disagreement within heterodox economics is lower than within mainstream economics; 3) some of commonly used ways of grouping heterodox and mainstream schools of thought have little explicative power in relation to individual opinions; 4) on critical economic policies, the opinions of heterodox and mainstream economists are significantly different even after controlling for a number of individual characteristics, including political opinions.