As new synthesis techniques are developed to create phosphors with smaller particles the physical processes that govern luminescence behaviors, like efficiency and decay rates, are influenced by the large surface-to-volume ratios of the nano-structured materials. Decay of lanthanide excited states, following pulsed laser excitation, is used to probe the affect of size-induced decay channels on the luminescent properties. We report results on the decay dynamics of europium and terbium excited states in solution-produced yttrium oxide. Radiative decay from the Eu 3+ 5 D 0 state is found to be well described by a single exponential function (τ=1.4ms) over a range of concentrations (0.01–2.0%). The Tb 3+ 5 D 4 decay exhibits a distribution of decay rates over the concentration range 0.01–5.0%. The distribution of decay rates is discussed using a probability density function based on the Kohlrausch decay function.