Voltage fluctuations analysis is one of the basic elements of power quality assessment in the power network. Presently, two voltage fluctuations measures are used-voltage fluctuations indexes and short-term Pst and long-term Plt flicker severity indicators. The voltage fluctuations indexes describe the variability of the root-mean-square (rms) value by means of the amplitude and the frequency. Pst and Plt indicators are used for the assessment of flicker obnoxiousness. This paper includes the comparison of both measures showing, beside definition differences, various diagnostic possibilities.