Aim: Breast cancer is one of the most common malignancies among women in Croatia and other developed countries. Various factors such as age, genetics, reproductive activity, diet, lifestyle, ethnicity and socioeconomic status contribute to the risk of developing breast cancer. Obesity is also considered a risk factor. This research focuses on the dietary habits and obesity of breast cancer patients in the Primorsko-goranska and Istria counties in Croatia, aiming to better understand their association with breast cancer. Methods:This study included fifty breast cancer patients from Primorsko-Goranska and Istria counties undergoing treatment at the Clinical Hospital Center Rijeka. The research was conducted from July 28th to August 28th, 2023, and involved measuring body components and completing a self-assessment MEDAS questionnaire. Results: The study included female participants from the Primorsko-goranska County (n=31, 62%) and Istria County (n=19, 38%). The participants had an average age of 62 years (ranging from 42 to 77), average height of 166.6 cm (ranging from 150 to 185), average weight of 74.7 kg (ranging from 46.2 to 105.7), and an average BMI (Body Mass Index) of 26.92 kg/m² (ranging from 18.5 to 39.3). The majority of participants were classified as overweight (64%) based on BMI distribution. Approximately 62% of participants had an elevated body fat percentage. The majority of participants (98%) had a normal level of visceral fat. The results of the MEDAS questionnaire indicated that the majority of participants (62%) had a good-quality diet and adherence to a Mediterranean diet. There were no statistically significant differences between the counties in the results of the MEDAS questionnaire based on the Chi-square test (p=0.20) and Mann-Whitney test (p=0.12). Similarly, there were no statistically significant differences in the distribution of BMI between the counties based on the Chi-square test (p=0.20) and Mann-Whitney test (p=0.21). There was not correlation between BMI values and the results of the MEDAS questionnaire. Conclusion: The research has shown that there is a link between obesity and breast cancer. The connection between dietary habits and breast cancer has not been established.