In this field report, we present and discuss methodological issues and challenges in questionnaire design in the context of ‘FReDA – The German Family Demography Panel Study,’ a family demographic mixed-mode panel study. We illustrate the transition from a questionnaire designed initially for the face-to-face mode to a self-administered mixed-mode survey design using web- and paper-based questionnaires. Aspects of questionnaire splitting and mode adaptations for web- and paper-based questionnaires are discussed with examples (e.g., ‘no opinion’ responses, item batteries, loop questions, and soft prompts). We compare the recruitment rate, panel consent rate, participation rate in the web-based mode, and the …