Median rest-frame effective radius (R_e; left) and Sérsic index (n; right) for optical and near-infrared parametric sub-samples as a function of redshift. The squares represent the median (and 1 − σ scatter) for redshift and morphological property (R_e, n) in a running median. On the x-axis we show the distribution of redshift for each optical and near-infrared sub-samples. For each sub-sample, in each panel, we show a linear parametric fit and 1-σ scatter. We also indicate the median size and Sérsic index from literature studies of SMGs (Swinbank et al. 2014; Gullberg et al. 2019). We identify larger (lower) effective radius (Sérsic index) at optical wavelengths compared to near-infrared measurements, with general a negative (∼2σ) correlation between the SMGs size and redshift whilst no strong correlation is identified with Sérsic index.