Scalable video coding is a promising solution for efficient video content distribution to users having heterogeneous network and terminal capabilities. Thanks to its inherent multidimensional adaptability, a scalable bit stream can be used to simultaneously transmit multiple video sequences having different bit rates to corresponding target users, without necessity of re-encoding or transcoding. In order to exploit such an advantage effectively, it is crucial to understand the effects of multidimensional scalability options on the perceived quality and the trade-off between the scalability dimensions through subjective quality assessment. This paper reviews existing studies aiming at achieving this goal in order to summarize their results and common findings.