This paper attempts to analyze the properties of a construction that is typical of Balkan languages, but is also encountered in non-Balkan Romance and Slavic, and a few additional languages. The construction, neutrally referred to as MEC (Modal Existential wh Construction), has the superficial appearance of a wh-clause, but the semantics of a narrow-scope existential generalized quantifier (GQ) such that the property expressed by IP has modal possibility/ability force. It is proposed, building on Grosu (1994), Grosu and Landman (1998) and Izvorski (1998), and modifying some of the views in these works, that MECs are non-core relative constructions consisting of a bare CP which carries the feature [GQ ∃ ], as well as a specification of its particular modality. Cross-linguistic distribution is captured by extensions of subcategorization options from nominal to CP arguments, such extensions being potentially 'licensed' by semantic-pragmatic properties of the matrix predicates in conjunction with the larger context, in the sense that such properties constitute necessary, but not sufficient, conditions for extension. The proposed analysis accounts for the upper bound on MEC distribution, for the kind of attested cross-linguistic variation, and for certain hitherto unaccounted for properties of MECs, in particular, an inability to serve as predicates, and a complete incompatibility with wh+ever-like phrases. 1 This paper could not have been written without the extensive help I received from a number of persons who generously provided information about their native languages and/or contributed substantive suggestions. Concerning the latter, I am profoundly indebted to Nirit Kadmon, who read several versions of this paper and offered suggestions that led to genuine improvements; concerning the former, I am grateful to