The control of synaptic inhibition is crucial for normal brain function. More than 20years ago, glycine and gamma-aminobutyric acid (GABA) were shown to be the two major inhibitory neurotransmitters. They can be released independently from different terminals or co-released from the same terminal to activate postsynaptic glycine and GABAA receptors. The anchoring protein gephyrin is involved in the postsynaptic accumulation of both glycine and GABAA receptors. In lower brain regions, both receptors can be concentrated in synapses, whereas in higher brain regions, glycine receptors are mostly excluded from postsynaptic sites. The activation of glycine and/or GABAA receptors determines the strength and precise timing of inhibition. Therefore, tight regulation of postsynaptic glycine versus GABAA receptor localization is crucial for optimizing synaptic inhibition in neurons. This review focuses on recent findings and discusses questions concerning the specificity of postsynaptic inhibitory neurotransmitter receptor accumulation during inhibitory synapse formation and development.