In surveys, which are a commonly accepted research method in social sciences, we always observe a certain percentage of respondents giving no-opinion responses such as “no opinion” or “hard to say”. In this study, we treat no-opinion responses as a motivated decision to refuse to respond. The aim of the study was to determine what factors involved in the organisation of a study increase the percentage of respondents who opt for no-opinion responses. The factors on which we focused include in particular the significance of the difficulty of questions; the order of questionnaire questions; motivating respondents through rewards, and the research technique. In the first part of the study, 575 students were divided into 5 groups. Each group was surveyed about environmental consumer attitudes in different survey conditions. In addition, the respondents were asked to rank the difficulty of individual questions in the survey. Findings: The study showed that the percentage of no-opinion responses increases as the questions become more difficult. The respondents were more likely to avoid stating their opinion on those unecological behaviours that they exhibited more frequently. The change of the research technique from a questionnaire to a direct interview caused a decrease in the percentage of noopinion responses. The respondents opted for a “no opinion” response less frequently when the interview was conducted by a lecturer than when it was conducted by a student. Changing the order of questions also affected the percentage of no-opinion responses; however, that was only true for questions that the respondents recognised as easy. Conclusions: The study showed that the choice of a research technique intended to reduce the percentage of no-opinion responses depends on the quality of questions. If they are difficult and require the respondents to engage cognitive resources, a better solution is to employ the direct interview method. However, if the questions are sensitive and the respondent may feel pressure to give a response that conforms to social norms, a better solution is to ensure them anonymity, e.g. by employing the questionnaire technique.