A memory card adaptor is provided which includes a housing including a bottom lid and a top lid that form the housing. The housing may be configured to receive a memory card. The memory card adaptor may include a package substrate between the bottom lid and the top lid. The package substrate may include a core having a first surface and a second surface; a first layer on the first surface, and the first layer may include a plurality of contact lands; and a second layer on the second surface, and the second layer may include a plurality of contact pads that are electrically connected with the contact lands through a plurality of via holes. The plurality of via holes may be formed such that they penetrate the core. One of the first and second layers may include a return path on at least one signal line.