Radiation curable compositions, such as UV curable ink compositions, contain a polymeric dispersant, a curable material, and a nanoscale pigment particle composition including an organic monoazo laked pigment including at least one functional moiety, and a sterically bulky stabilizer compound including at least one functional group, wherein the functional moiety of the pigment associates non-covalently with the functional group of the stabilizer; and the presence of the associated stabilizer limits the extent of particle growth and aggregation, to afford nanoscale-sized pigment particles.