The article is devoted to the problem of survey items that ask for sensitive information. This factor has a significant impact on the quality and comparability of data from international surveys. We propose a methodology that can be used to comparatively study the level of sensitivity of questions. It is often used in public opinion polls as well as in marketing and academic studies. We were able to use it to identify similarities and differences in what questions are considered sensitive by the different populations of the nine countries of the former Soviet Union as a whole as well as among particular socio-demographic groups. The study analyzes the reasons why certain questions are considered to be sensitive: the violation of various norms, whether legal or political, social or moral, communication etiquette or beliefs about what constitutes private information. We developed a classification of sensitive questions based on the reasons that were identified. The obtained results allow us to better understand the reasons of why certain questions are considered to be sensitive, to develop an approach to how this concept should be defined, and to identify the differences between sensitive questions and those that are perceived to have other qualities, such as those that are "threatening" and questions fraught with social desirability effect. The results of this comparative study can be used to improve the tools and to allow a deeper analysis of cross-national survey data. [This article was translated by Kenneth Cargill.]