An inadequate diet and lifestyle are major causes of various diseases. A healthy diet can prevent diseases and maintain a good health status. The present research objective was to test young consumers for their preference for healthy diets and their intention to purchase functional foods, as well as to identify factors that affect their attitudes. The study involved 720 consumers (average 20 years old), a structured questionnaire, and a specially-developed scientific methodology. The results were grouped based on sex and body mass index. The analysis focused on the points where consumers’ interest in healthy diet overlapped with health-related diet needs and how each of them corresponded with their knowledge on the following spheres: nutrition and health risks, labelled data use in food choice, preference for foods fortified with vitamins, minerals, dietary fibers, or functional foods with a poor sensory quality. The data were processed using descriptive statistics, Z-test, and correlation tests. All the consumers demonstrated healthy diet preferences and a significant positive relationship (p < 0.01) with the factors. They made an informed choice based on the labelled data and preferred foods fortified with vitamins, minerals, and dietary fibers, as well as functional products with a lower sensory quality. All respondents, regardless of sex and body mass index, demonstrated nutrition and health risk awareness. The health-related diet needs also affected their food preferences (p < 0.05), with some exceptions. The young consumers possessed sufficient basic knowledge on food quality, nutrition, and health. Their attitudes depended on their preference for healthy diets and functional foods. The novel methodology can be applied to other studies of consumer preferences.