One crucial component for synaptic functionality is the proteome within the spines, which is fueled by local mRNA translation and the influx of proteins from the dendrite. A neuron could recruit proteins from the dendritic pool or increase local synthesis to increase the protein number at the synapses. However, since only about 10-20% of proteins have local mRNAs in the dendrites, the question arises; how do the other 80-90% of dendritic and synaptic proteins dynamically control their copy numbers without having the ability to increase the synthesis rate of the protein of interest locally. We tested the hypothesis that the size of the dendritic pool of proteins is related to the presence or absence of dendritic mRNAs. Thus, if a protein species can’t be synthesized on-demand in the dendrite or synapses because it lacks local mRNAs, it must compensate with a larger dendritic “stand-by” pool of proteins. Therefore, the size of dendritic pool relative to synaptic population needs to be larger for proteins that lack dendritic protein synthesis. We analyzed experimentally reported protein and mRNA localization profiles to test this hypothesis and developed a mathematical model to describe neuronal mRNA and protein distributions. Our results confirm our hypothesis that dendritic protein synthesis is negatively correlated with the size of the dendritic protein pool, indicating a preferential establishment of a dendritic “stand-by” protein pool in species lacking dendritic mRNA translation. Our results offer a new perspective on the mechanisms establishing the diversity of molecular distributions in the dendrites.