The process of data updating in the databases of the Internet decision support system for cereals protection is presented. The system uses three kinds of data: on spring and winter wheat varieties, on plant protection products (fungicides and insecticides against wheat diseases and pests) and on product doses. It was found that it is possible to obtain all the necessary data for the updating from available web resources. Data sources for variety information are the COBORU materials and websites of agricultural plant breeders. The search engine of plant protection products available on the website of the Ministry of Agriculture and Rural Development is an essential source of the data on protection products and their doses. Other sources of these data are websites of plant protection product producers and online shops. In the data updating process the following stages were distinguished: owned-resources stocktaking, data quality criteria selection, credible data sources determination, data acquisition by the application of the criteria, data adaptation to the system requirements, data entry, data verification. Each one of the itemized stages contributes to the ultimate data quality after the updating. The stages of credible data sources determination, data acquisition and data adaptation to the system requirements were found to be labour intensive. About a triple reduction of labour input into the updating was achieved through the improvement of the data acquisition process, gaining proficiency in the database editors operation and the cumulative effect of build-up of specific data resources in the system. The adopted verification procedures for update correctness are described.