Based on the literature-derived data on (co-)gasification, this paper aims to compare syngases obtained by steam gasification of different feedstocks (e.g. biomass, polyethylene, waste tire and coal) either single or mixed. The comparison among syngases was based on the variables that described the quality (i.e. content of H-2, CO, CH4 and CO2, H-2/CO, H-2 + CO), main operational parameters (gasification temperature, feeding ratio, scale of the gasification equipment) and the feedstock composition. These variables were summarized in two data sets and assessed by principal component analysis (PCA) in order to examine which of them have more determinant influence on differentiation of syngases produced by steam gasification of different feedstocks. Under wide range of gasification conditions considered in the study, syngases differed particularly in CH4 content and H-2/CO, while the lowest variability was observed for H-2 content. PCA revealed clear separation between syngases produced by gasification of single feed materials and those by co-gasification of the mixed feedstocks. Gases produced by mixed feed materials gasification had higher contents of CO2 and CO, while higher H-2 contents, H-2/CO and (H-2 + CO) values were linked with coal and tire processing. The observed outliers (not belonging to either of the separated groups) were syngases produced from tire under unique conditions compared to other considered systems (high temperature (1000 degrees C) or mixed gasifying agents).