The sound category of the vowel quantity is applied in the structure of languages in different ways, and its adaptation from one system to another is difficult. The subject of the paper is the difficulties Russian speakers have in the production of Czech texts with more long vowels in a row, i.e., in a situation that does not exist in Russian.
Sample of Czech created for the purpose of the experiment and recorded by Russian and Czech native speakers serve as the basis. The success in the realization of quantity in Russian speakers as assessed by Czech native listeners was monitored, and the duration values of short and long vowels and their ratio in the speech of Russian and Czech speakers were compared.