This paper investigates the syntactic behaviors of zenmeyang ‘how’ and weishenme ‘why’ in Mandarin Chinese. Essentially, there are two asymmetries about these two adjuncts that must be accounted for, i.e., (a) the asymmetry with regard to their distributions in simplex sentences and long-distance extraction in complex constructions and (b) the asymmetry between extraction of weishenme from the complement clause of conjecture verbs and from the complement clause of opinion verbs. In this article, we show that while zenmeyang is base-generated within VP, weishenme is base-generated in the Spec of CP. This structural difference, coupled with a conjunctive formulation of the ECP and the assumption that intermediate traces are not subject to it, leads to the asymmetry between these two adjuncts with regard to long-distance extraction. As for the second asymmetry, we suggest that it comes from a strong/weak distinction of Comp; while a strong Comp, i.e., a Comp that can be lexically filled by question particles, may function as a head governor, a weak Comp may not. In addition to the preverbal zenmeyang, the descriptive/resultative postverbal zenmeyang ‘how’ is discussed and shown to be no different from the former with regard to long-distance extraction. A-not-A questions are also reanalyzed within our theory as a complete analogue to weishenme ‘why’.