Abstract. This paper is focused on the process of computing First Sets. The First Sets are used to build structures which control a syntax analyser (also known as parser). Three methods of creating First Sets were compared in terms of execution time. The first method is known sequential algorithm and the author's own methods are concurrent computing sets for each non-terminal symbol (called the CEN method) and concurrent computing sets for each production (called the CEP method). These methods have been tested on personal computer. Three programming languages (including the C language) were used in the research. The results and the analysis of calculations allow the author to hypothesise that the problem of computing First Sets is hard to concurrence.