The issue of the luminous flux radiation to the upper hemisphere is very broad and complex. The paper deals with the modelling of the vertical surface radiators. It presents an approach to unify the behaviour of these types of light sources. These will be understood as cosine radiators. If this cosine distribution curve is taken into account, then only the luminance and the light-active surface can be known to supplement the information about the radiation of such the light source. The luminance and radiated surface can be obtained relatively easily from real field measurements. The article presents the implementation of this data into lighting calculations and the creation of the distribution curves which are necessary for the radiation calculations of these surfaces. It also analyses the influence of the luminance and active areas on the radiated luminous flux and assign these values to the real radiators.