In this study, determination of fluorine in water samples was established via the rotational fine structured molecular absorption of calcium mono-fluoride (CaF) at 606.440 nm using a high-resolution continuum source electrothermal atomic absorption spectrophotometer. To generate CaF in the gas phase of graphite furnace, samples were pipetted together with calcium as its nitrate form. The effect of amount of calcium, graphite furnace program, coating the graphite tube and platform with Zr and Ir and the use of modifier (Pd, Mg and Pd+Mg) on the sensitivity and linearity were investigated. In the presence of 40 mu g of Ca, a perfect linearity up to 0.1 mu g of F was maintained applying a pyrolysis temperature of 700 degrees C and a molecule forming temperature of 2250 degrees C in pyrolytically coated platforms. The limit of detection and characteristic mass of the method were 0.21 ng and 0.13 ng of F, respectively.