Since the seminal work by Brandi & Cordin (1981; 1989), the syntactic differences between subject clitics in Italian dialects (Trentino and Fiorentino) and subject clitics in French have been assumed to rely on the value of the null subject parameter: subject clitics in Italian dialects behave like verbal affixes; that is, they do not realize a specific position but should be considered as verbal morphology. Subject clitics in French realize the structural position for the subject connected with nominative case assignment. The Germanic-Romance comparative perspective allows us to provide a more complex picture. On one hand, the difference between ‘weak pronouns’ and clitics could be better understood: ‘weak’ German pronouns in the so-called Wackernagelposition are not morphologically distinct from full pronouns and cannot double the subject, but they present some analogies with French clitics rather than with clitics in Italian dialects. On the other hand, subject clitics in Germanic varieties such as West Flemish and Bavarian, and even in isolated varieties such as Cimbrian, differ strongly from their Romance counterparts with regard to both finite verb movement and nominative case assignment, and have been analyzed as being either agreement morphology in C or nominative case markers. The consideration of all the factors involved in the definition of ‘subject clitic’ allow us to define the feature characterization of the hosting head, which acts as a probe for the cliticization process, and to re-evaluate the traditional distinction between comp-dominant versus infl-dominant languages through the distinction between phase versus non-phase head.