Institutional Italian is a variety of Italian used in the official communications of institutions, especially in public administrations. Besides legal and administrative languages, it comprises the language used in websites, social media and advertising material produced by public administrations. To understand the lexical profile of institutional languages completely, standard measures of lexical complexity, like the type-token ratio and the percentage of basic vocabulary, should be complemented with the examination of the terminological variation. This study compares the terminology of three types of institutional texts: administrative acts, technical-operational texts, and informative texts. In particular, we collected 86 terms with various degrees of specialization and analysed their distribution within the subcorpora of ItaIst-DdAC_GRU, a corpus composed of institutional texts drafted by Italian municipalities about municipal waste management. Results suggest that administrative acts employ high-specialization terms compliant with the law, often in the form of acronyms. Conversely, informative texts contain more low-specialization terms, privileging single-word terms to remain self-contained. Finally, the terminology of technical-operational texts is characterised by standardized and formulaic phrases.