This dataset contains the data and experimental code used in the study: Filip, T., Pavlíček, M., & Sosík, P. (2024)."Tuning of language models in Eastern European languages on Twitter/X."In Proceedings of the Workshop on Artificial Intelligence and Language Technologies (Vol. 4092). CEUR-WS. The dataset includes:– text data from multiple Eastern European V4 languages collected from Twitter/X,– preprocessing and cleaning scripts,– experimental code used for training and evaluation,– evaluation outputs (metrics, tables, plots),– all resources required to reproduce the results presented in the article. This dataset serves as supplementary material to the publication referenced above. Funding acknowledgment:This work has been produced with the financial support of the European Union under the "Biography of Fake News with a Touch of AI: Dangerous Phenomenon through the Prism of Modern Human Sciences" project no. CZ.02.01.01/00/23_025/0008724 via the Operational Programme Jan Ámos Komenský (OP JAK).