Knowledge of genetic relationship is an important control mechanism for animal performance-testing schemes. Genetic relationship between and within pig herds was calculated for two dam breeds, Czech Large White (CLW) and Czech Landrace (CLA). The impacts of different field data types (production and reproduction) and various numbers of generations within the pedigrees on genetic relationship were studied. The degree of genetic relationship between analyzed herds was generally low. It ranged from 1.01% (for CLW based on reproduction data and considering three generations of ancestors within the pedigree) to 2.57% (for CLA based on production data with seven generations of ancestors in the pedigree). In contrast, relationship within herds was high and ranged from 16.62% to 44.69% (when three and seven generations within the pedigree were taken into account, respectively), both for production data of the CLA breed. When considering the type of data, an impact on the observed genetic relationship between and within herds was found. Slightly higher genetic relationship between herds was determined in both breeds when using production data (1.64%) compared to reproduction data (1.40%). In contrast, a negligible influence between herds on genetic relationship was found from the number of ancestors’ generations included into the calculations. That was especially so after five or six generations. Our results show that the relationship between herds is population specific and, consequently, must be analyzed on a case-by-case basis. Knowledge of genetic relationship between and within herds should be taken into account in regard to the complexity of genetic evaluation.