To define the dermoscopic aspects of the network in melanoma in situ (MIS), using both standard and newly introduced network descriptors. Fifty-four histologically confirmed MIS with a reticular pattern, 108 atypical reticular naevi and 108 typical reticular naevi were evaluated for the presence of 11 network descriptors. The ABCD-score and the seven-point score were calculated, and the diameter of the lesions was measured by means of a dedicated software. Clinical data including age, sex and skin site were also considered. The prevalence of different dermoscopic features was calculated to allow (i) the identification of lesions to be excised and (ii) the distinction between MIS and dermoscopically atypical naevi. In dermoscopically atypical lesions (MIS and atypical naevi), the frequency of all descriptors significantly differed from those of typical naevi. With respect to atypical naevi, MIS more frequently showed larger size, an atypical network involving more than half of the lesion, the contemporary presence of more than one type of network and more extended reticular grey–blue regression areas located both in the centre and at the periphery of the lesion. The list of network descriptors proposed by us can be used for the identification of lesions that should be subjected to surgery. For the distinction between MIS and atypical naevi, the extension of an atypical network, the presence of more than one type of network, the distribution of reticular grey–blue areas and the lesion diameter must be considered.