A simple method based on hydrolysis of 2,3-dicyanopyrazinium salts has been used for the synthesis of the corresponding 5-(hetero)aryl-3-cyano-1-ethyl-2(1H)-pyrazinones. Also, the series of novel 1-ethyl-5-(hetero)aryl-1,6-dihydropyrazine-2,3-dicarbonitriles have been obtained through reduction of the same pyrazinium salts with triethylsilane. The obtained compounds proved to be active in micromolar concentrations in vitro against Mycobacterium tuberculosis H37Rv, Mycobacterium avium, Mycobacterium terrae, as well as against rifampicin and isoniazid-resistance strains of Mycobacterium tuberculosis. The data for acute in vivo toxicity in mice have been obtained for these compounds which appear to be promising antitubercular agents