Studies on L1- and L2-acquisition of German and Dutch have shown that the particles "too/also" and "again" hamper the realization of finiteness while the particle "not" promotes it. In this study the authors ask whether adversative "but" also affects the realization of finiteness. By applying a structural-functional approach to finiteness and its acquisition they investigate the morpho-syntactic development of "aber"-clauses in the first 12 months of "aber"-production in four monolingual German children. The analysis reveals that finiteness becomes realized in "aber"-clauses considerably later than in "auch"-clauses. Syntactically well-formed "aber"-clauses appear when finiteness becomes realized in main clauses not containing any particle or connective. However, it takes the children two to four more months to realize finiteness in the "aber"-clauses. The authors argue that the information-structural properties assumed to cause the delay raised by the particles "too/also" and "again" are not fully applicable to "but." Particle-specific effects also have to be taken into consideration. In case of "but" this includes the complexity of information-structural alignment and discourse integration of the twofold contrast established by "aber"-clauses. Managing this communicative task reduces the capacities for realizing primarily structural conditions which are still not automatized.