The novel availability of exotic nuclei has spurred an immense revival of nuclear structure investigations . Indeed nuclei close to the neutron or proton drip lines may exhibit very unusual features such as pronounced neutron or proton skins , and neutron halos . Among many very interesting questions, nuclear pairing has again become on the forefront of theoretical interest. Indeed the existence of neutron halos is due to the pairing force [4,5] and in heavier proton rich N ' Z nuclei the proton-neutron pairing may play an important role . In this work we therefore want to address some problems of neutron-neutron and proton-neutron pairing. This concerns for instance considerations of the effective pairing interactions. However, we also will discuss some other aspects of more general character. We mostly will study the infinite matter case.