Existence theorems are given for the problem of finding a point (z0,x0) of a set E × K such that \documentclass[12pt]{minimal}
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\begin{document}$$(z_0,x_0)\in B(z_0,x_0)\times A(z_0,x_0)$$\end{document} and, for all \documentclass[12pt]{minimal}
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\begin{document}$$\eta\in A(z_0,x_0), (F(z_0,x_0,x_0,\eta), C(z_0,x_0,x_0,\eta))\in \alpha$$\end{document} where α is a relation on 2Y (i.e., a subset of 2Y × 2Y), \documentclass[12pt]{minimal}
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\begin{document}$$A : E\times K\longrightarrow 2^K,$$\end{document}\documentclass[12pt]{minimal}
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\begin{document}$$B : E\times K\longrightarrow 2^E, C : E\times K\times K\times K\longrightarrow 2^Y$$\end{document} and \documentclass[12pt]{minimal}
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\begin{document}$$F : E\times K\times K\times K\longrightarrow 2^Y$$\end{document} are some set-valued maps, and Y is a topological vector space. Detailed discussions are devoted to special cases of α and C which correspond to several generalized vector quasi-equilibrium problems with set-valued maps. In such special cases, existence theorems are obtained with or without pseudomonotonicity assumptions.