The optical properties of chromophoric dissolved organic matter (CDOM) in Danish estuaries and coastal waters were investigated. A new method for estimating the spectral slope coefficient (S) was examined and found to give a closer fit for the measured absorption (92% reduction in sum of residuals) than the traditional method. The spectral pattern in residuals produced by the new technique enabled the identification of CDOM originating from areas of different land uses/types where S coefficients were similar. S values were found to behave conservatively with respect to salinity in all waters except for the off-shore North Sea region where CDOM from marine sources was suspected to have more influence. The specific absorption coefficient of CDOM did not vary significantly in Danish coastal waters. These waters are of particular interest in bio-optical studies as they allow the study of CDOM across a gradient from estuarine, brackish to near-oceanic environments. The results demonstrate that it is possible to develop regional models for the optical properties of CDOM which would then allow higher precision in remote sensing applications.