Optional constituents of a clause which, according to a couple of criteria, are commonly called parentheticals show quite diverging properties with respect to structurally determined aspects of constituency and interpretation like constituent placement, scope, bound variable reading of pronominals. One type of parenthetical strings may form regular constituents of a clause, if the string is not parenthetically marked, and shows the same facts about interpretation like other regular constituents. The other type may not. Strings of the former type have to be represented as parts of their host at both levels of syntactic representation C-structure and F-structure. Parentheticals of the latter type must be treated in a different way, since they exhibit properties usually attributed to strings which are not constituents of the host. I will propose an analysis of this type which rests on the integration of the parenthetical string into the C-structure of the host but its separate non-integrated representation at F-structure.