Zero frequency resonator (ZFR) was proposed earlier for the extraction of glottal closure instants (GCIs) (Murty and Yegnanarayana 2008). The output of ZFR is an exponentially growing/decaying signal. The trend of this signal can be removed to get the required resolution for detecting relevant information. By considering a window size of typical 1–2 pitch periods, the trend removed signal mainly exhibits information related to GCIs. This work proposes two methods for the detection of glottal opening instants (GOIs) using ZFR. In the first method, the window size for trend removing is reduced to a lower level (say, 0.33 × pitch period), and the possibility of hypothesizing GOIs is demonstrated. In the second method, window size remains in the range of 1–2 pitch periods, but the input to ZFR is modified to remove GCIs information. The proposed methods are evaluated using CMU-Arctic database and compared with existing methods for GOI detection. The performance for the detection of GOIs is comparable to that of GCIs and also existing methods. © 2016, Springer Science+Business Media New York.