The document summarizes a study that compared data collected via web surveys versus telephone surveys (CATI) for candidates in Greek political parties. Some key findings were: - Age and year of birth showed significant differences between the two modes, but education and income did not. - For most issues and policies there were significant differences in responses between the two modes, but these differences were reduced after matching respondents. - Direction of responses (e.g. agree vs disagree) were similar between modes, but intensity of responses sometimes differed significantly. - Recency and acquiescence effects may have driven some CATI respondents to choose the last response option more frequently compared to web respondents.