The aim of this research was to examine the effect of the bandwidth on parameters that are used to quantify glottal airflow waveforms that have been obtained by inverse filtering the acoustic signals. Three bandwidths (1, 2, and 4 kHz) were compared using /a/ vowels of different phonation types. Glottal waveforms were characterized using three ratios computed from the flow (open quotient, speed quotient, and closing quotient) and two parameters extracted from the differentiated flow (the amplitude of the negative peak and the return time from the negative peak to zero level). The results show that especially in pressed phonation the bandwidth should be at least 4 kHz. Distortion caused by an insufficient frequency range was most severe in the parameters extracted from the flow derivatives. Among the parameters computed from the flow signals, the closing quotient was affected most when the bandwidth was reduced.