© 2017 Elsevier Inc. This paper is motivated by a long-standing conjecture of Dinculeanu from 1967. Let X and Y be Banach spaces and let ? be a compact Hausdorff space. Dinculeanu conjectured that there exist operators S?L(C(?),L(X,Y)) which are not associated to any U?L(C(?,X),Y). We study this existence problem systematically on three possible levels of generality: the classical case C(?,X) of continuous vector-valued functions, p-continuous vector-valued functions, and tensor products. On each level, we establish necessary and sufficient conditions for an L(X,Y)-valued operator to be associated to a Y-valued operator. Among others, we see that examples, proving Dinculeanu's conjecture, come out on the all three levels of generality.