The paper is focused on genomic breeding values ​​for resistance to clinical mastitis in Holstein cattle. First dataset included 18,633 cows with 22,179 lactations. It was created by using a national web application “The Diary of Diseases and Medication” (the Diary). The comparison was carried out with a dataset based on the Diary and supplemented by Q CZ on-line survey for time period from July 2016 through June 2017. This dataset included 29,505 animals and 49,044 lactations. A linear animal model was employed for estimation of breeding values. A single-step procedure for genomic evaluation was used for estimaton of genomic breeding values, simultaneously using all sources of information about the population. Relative breeding values ​​for both conventional (RPH) and genomic ((GE)RPH) breeding values ​​were calculated from the estimates obtained. As a reference level, the average of conventional or genomic breeding values ​​of sires born in 2010 was used. The higher the relative breeding value, the higher the breeding value of the animal for resistance to clinical mastitis. The reliability of the breeding values ​​was calculated based on standard estimation errors and additive genetic variation estimated for clinical mastitis. Heritability coefficients of clinical mastitis was 2.85% (the Diary) and 4.97% (the Diary + Q CZ). The values of heritability correspond to commonly published results. It has been shown that the use of Q CZ as well as genomic estimation leads to an increase in the reliability of breeding values. Therefore, we suggest to continue to use the dataset including Q CZ data and single-step procedure for genomic evaluation to estimate breeding values ​​for clinical mastitis resistance.