CDOM sorption to particles has significant implications for the biogeochemistry of the water column and possibly the optical properties of the hydrosol as well. There is growing evidence that a substantial fraction of coastal organic matter is tightly associated with suspended minerals and that some portion of this organic material may be attributable to colored humic substances. How the absorption and fluorescence associated with CDOM are transferred to the particulate fraction and what the resulting effects are on the bulk optical properties are not well known. The interaction may alter the physicochemical nature of the organic material and thus its optical properties. Adsorption onto particles will also package the colored material, which could result in a self-shading effect, decreasing bulk absorption of light. The scattering properties of the particulate fraction may also be altered due to the effects of absorption by the organic coating and the disparate refractive indices of the coating and the particle. These issues are investigated with laboratory work and theoretical modeling. The overall importance of CDOM adsorption on the optical properties of the bulk dissolved and particulate fractions in coastal waters is evaluated.Twardowski, M. and E. Boss, 2002. The Optical Effects of CDOM Sorption to Particles. Presented at AGU-ASLO, Hawaii, Feb.