We study the relationship between weak* Dunford–Pettis and weakly (resp. M-weakly, order weakly, almost M-weakly, and almost L-weakly) operators on Banach lattices. The following is one of the major results dealing with this matter: If E and F are Banach lattices such that F is Dedekind $\sigma $-complete, then each positive weak* Dunford–Pettis operator $T:E\rightarrow F$ is weakly compact if and only if one of the following assertions is valid: (a) the norms of $E^{\prime }$ and F are order continuous; (b) E is reflexive; and (c) F is reflexive.

It is proved that if a positive operator $S\,:\,E\,\to \,F$ is $\text{AM}$-compact whenever its adjoint ${{S}^{'}}:{{F}^{'}}\to {{E}^{'}}$ is $\text{AM}$-compact, then either the norm of $\text{F}$ is order continuous or $E\prime $ is discrete.

We study the duality problem for order weakly compact operators by giving sufficient and necessary conditions under which the order weak compactness of an operator implies the order weak compactness of its adjoint and conversely.

We prove the converse of a theorem of Zaanen about the duality problem of positive $\text{AM}$-compact operators.