Lung cancer in men and breast cancer in women are the most commonly diagnosed cancers in Poland and worldwide. Results of studies involving dietary patterns (DPs) and breast or lung cancer risk in European countries outside the Mediterranean Sea region are limited and inconclusive. This study aimed to develop a 'Polish-adapted Mediterranean Diet' ('Polish-aMED') score, and then study the associations between the 'Polish-aMED' score and a posteriori-derived dietary patterns with breast or lung cancer risk in adult Poles. This pooled analysis of two case-control studies involved 560 subjects (280 men, 280 women) aged 40-75 years from Northeastern Poland. Diagnoses of breast cancer in 140 women and lung cancer in 140 men were found. The food frequency consumption of 21 selected food groups was collected using a 62-item Food Frequency Questionnaire (FFQ)-6. The 'Polish-adapted Mediterranean Diet' score which included eight items-vegetables, fruit, whole grain, fish, legumes, nuts and seeds-as well as the ratio of vegetable oils to animal fat and red and processed meat was developed (range: 0-8 points). Three DPs were identified in a Principal Component Analysis: 'Prudent', 'Non-healthy', 'Dressings and sweetened-low-fat dairy'. In a multiple logistic regression analysis, two models were created: crude, and adjusted for age, sex, type of cancer, Body Mass Index (BMI), socioeconomic status (SES) index, overall physical activity, smoking status and alcohol abuse. The risk of breast or lung cancer was lower in the average (3-5 points) and high (6-8 points) levels of the 'Polish-aMED' score compared to the low (0-2 points) level by 51% (odds ratio (OR): 0.49; 95% confidence interval (Cl): 0.30-0.80; p < 0.01; adjusted) and 63% (OR: 0.37; 95% Cl: 0.21-0.64; p < 0.001; adjusted), respectively. In the middle and upper tertiles compared to the bottom tertile of the 'Prudent' DP, the risk of cancer was lower by 38-43% (crude) but was not significant after adjustment for confounders. In the upper compared to the bottom tertile of the 'Non-healthy' DP, the risk of cancer was higher by 65% (OR: 1.65; 95% Cl: 1.05-2.59; p < 0.05; adjusted). In conclusion, the Polish adaptation of the Mediterranean diet could be considered for adults living in non-Mediterranean countries for the prevention of the breast or lung cancers. Future studies should explore the role of a traditional Mediterranean diet fitted to local dietary patterns of non-Mediterranean Europeans in cancer prevention.