This paper will deal with the topic of analysis of the decision-making process in purchase, i.e. which items influence consumers when deciding what to buy and the process they are going through during the decision-making process. The first part of the paper will explain who the consumer is, since there is a clear distinction between them and customers, what types of consumers exist in certain markets and what factors affect consumer behaviour. In short, factors affecting consumer behaviour are divided into four parts, and can be psychological, personal, social and cultural factors. The second part brings us what kind of markets there are in which consumers buy and how the market affects consumer decisions. There are two basic types of markets on which consumers buy, namely the final consumption market and the business consumption market. Both markets possess certain characteristics on the basis of which they differ and there are certain patterns of consumer behaviour that occur in each of these markets. The third part refers to the very process of making a purchase decision, where the stages of this process are explained in more detail. The phases are awareness of the need, finding information, assessing alternatives, purchasing decisions and consumers' post-purchase behaviour. Finally, there is a detailed analysis of the process of making a purchase decision based on the research carried out on this topic. It also provides a conclusion, a list of literature, pictures and graphs and a questionnaire survey.