  According to T. Foguel a subgroup $H$ of a group $G$ is called
conjugate-permutable if $ HH^x=H^xH$ for every $x\in G$. Mingyao Xu and Qinhai
Zhang studied finite groups with every subgroup conjugate-permutable
(ECP-groups) and asked three questions about them. We gave the answers on these
questions. In particular, every group of exponent 3 is ECP-group, there exist
non-regular ECP-$3$-groups and the class of all finite ECP-groups is neither
formation nor variety.
