ABSTRACT Purpose This short presentation aims to indicate phonological features inherent to the sonorant consonant class (nasals and liquids) that might be relatively problematic in the orthographic records of these phonemes. Methods orthographic replacement in text compositions from children in the first grade of elementary school was analyzed. Data analysis was performed according to the Padrão de Aquisição de Contrastes (PAC). Results Results reveal that replacement was distributed between the two classes, and within each subclass, relatively unstable phonological contrasts were detected in the orthographic records of these phonemes. Conclusion This relative instability of contrasts pointed out phonological issues, as well as issues related to the orthographic complexity of each these segments, thus indicating a non-direct relation between speech and spelling.