Abstract : We point out a strong influence of the pairing force on the size of the two-neutron Cooper pair in 11Li, and to a lesser extent also in 6He. It seems that these are quite unique situations, since Cooper pair sizes of stable superfluid nuclei are very little influenced by the intensity of pairing, as recently reported. We explore the difference between 11Li and heavier superfluid nuclei, and discuss reasons for the exceptional situation in 11Li.