A structural study of graphene oxide complexes with detonation nanodiamonds (particle size 4–5 nm, positive surface potential) in aqueous suspensions by small-angle neutron scattering is reported. While the pure graphene oxide suspension exhibits a completely planar structure, the grafting of detonation nanodiamond particles results in a slightly curved surface of the graphene oxide flakes. The complexes “graphene oxide–detonation nanodiamonds” washed out from free detonation nanodiamonds show that the effective curvature of the graphene oxide plane is the result of binding of detonation nanodiamonds in the form of planar aggregates.