Modular buildings are built using factory manufactured building units or modules that are transported and assembled on-site. Among the many different types of building units used, volumetric modules have the greatest potential to achieve complete building systems, where on-site work can be reduced to having only foundation, module assembly and the finishing of module-to-module interfaces. However, despite many reported benefits, the use of volumetric modules have some technical, logistical and regulatory issues that constrain its widespread application. The aims of this paper is to articulate two key technical issues that have been widely reported, namely, the lack of efficient structural systems for lateral load transfer and the lack of high-performance inter-module connectivity. Accordingly, a general overview regarding these two issues is presented that covers the behaviour of diaphragms in multi-story modular buildings and the essential characteristics required for inter-module connections. It is expected that inter-module connectivity should meet structural needs along with satisfying manufacturing and construction requirements. Brief descriptions of existing inter-module connecting systems that are available in both literature and the public domain including a critical review of those connections against the identified performance requirements are also presented. The outcomes of this paper are expected to assist in the future development and application of fully-modular superstructure construction systems for multi-story modular buildings.