The effects of seeing on the parameters of the Sèrsic profile are studied in an analytical form using a Gaussian point spread function .
The surface brightness of Sèrsic profiles is proportional ( in magnitudes ) to r ^ { 1 / n } .
The parameter n serves to classify the type of profile and is related to the central luminosity concentration .
It is the parameter most affected by seeing ; furthermore , the value of n that can be measured is always smaller than the real one .
It is shown that the luminosity density of the Sèrsic profile with n less than 0.5 has a central depression , which is physically unlikely .
Also , the intrinsic ellipticity of the sources has been taken into account and we show that the parameters are dependent when the effects of seeing are non-negligible .
Finally , a prescription for correcting raw effective radii , central intensities and n parameters is given .