Modern mediatext as a new communication product of the publicistic discourse opens wide per-spectives to research semantic-derivative dynamics of the vocabulary of the German language. The major component of the German mediatext is a headline. Mediatexts may generally feature two types of headlines: thematic headlines and slogans, the latter are more likely to comprise modified phraseological units. Phraseological modification refers to the process of occasional (situational and textual) changes of the form and meaning of the phraseological units. Such pragmatically conditioned variations of set expressions from standard form and meaning result in abnormalities in structural unity regarded as inherent feature of the phraseological units, i.e. ready-to-use princi-ple. However, these variations comply with the principle of idiomaticity and so-called “psychologi-cal stability”, in other words, idioms are firmly fixed as a distinctive complex unit in our mental lexicon. There are various modification mechanisms (substitution, expansion) by which modified phraseological units are incorporated in the text; such variations unlock potential of the idioms as a text construction factor.