We investigate the morphologies, masses and possible correlations between these two properties for 108 extremely red galaxies (EROs) found in the Groth strip. The photometric data include U, B, F606W, F814W, J, and K_s bands. The EROs were selected on the basis of their extremely red colour, F814W-K_s ≥ 4 and K_s ≤ 21.0. Morphologies are based on a by eye classification and we distinguish between 3 basic classes: compact objects, targets with a disc and/or a bulge component, and irregular or merger candidates. An additional group consists of the few objects which could not be classified. The majority of our targets has either a very compact morphology (37 ± 6%), or show more or less distinct disc components (39 ± 6%). 13 ± 3% are merger or irregulars and a small number of objects (approximately 10%) could not be classified.As found in previous studies, most the EROs in our sample have redshifts between z=1 and z=2; however, compact EROs in our sample are found at redshifts as low as z=0.4 and as high as z=2.8; the latter qualify as well as distant red objects (DRGs). Disky EROs are also found up to z=2.8; however those with a bulge-like nucleus are only seen at z<1.5.For each of these EROs we determined the stellar mass and mean population age by fitting synthetic spectra (Bruzual 2007, IAU Symp., 241, 125) to the photometric spectral energy distributions, via χ^2 minimisation. Mass estimates were obtained by assuming an exponentially declining star formation rate with a wide set of parameters, e.g. decay time, redshift of last star formation, metallicity, and optical depth. Total stellar masses for our sample are in the range 9.1 < log(M_*/M_&sun;) < 11.6. We cannot detect significant differences between the stellar mass distribution of the morphological classe, i.e. the median stellar mass seems independent of morphology. However, above log(M_*/M_&sun;) > 11.0 galaxies dominantly show compact morphologies. We do not observe a strong evolution within 1 10^{11} M_&sun; detected in the DEEP2/Palomar fields. The EROs within their K<19.7 selection have the same upper range of masses at z ≈ 0.8-2.0, indicating little mass growth for this population at this K-band limit. We also detect a substantial fraction of EROs with total stellar masses below 10^{11} M_&sun;, while Conselice et al. state that almost all of their EROs at K<19.7 have masses above this limit.