This paper proposes novel mechanisms to access sensory data in a distributed fashion in 3D wireless sensor networks. As these networks have their nodes deployed in 3D volumes, we first propose a volume parametrization algorithm to transform irregular volumes into a regular one; it also allows us to extend network protocols from 2D to 3D (which would otherwise be highly non-trivial). Based on this transformation, we propose a new quorum system, 3DQS, to handle distributed data access. The tunability of 3DQS enables it to adapt to different application requirements. We demonstrate the efficacy and efficiency of 3DQS through both analysis and simulations.