This study tested whether and how methods called 'Play Time/Social Time' and 'I Can Problem Solve' contribute to the improvement of social skills and the development of theory of mind (ToM) in children. The participants in the experiment were nearly 200 (N = 196) preschool children with low social functioning, with and without disabilities. The study showed that social skills and the level of ToM in children attending the lessons improved more than those of children from the control group. Both methods turned out to be effective in the case of social skills and ToM development among children with and without disabilities. It is worthwhile to popularise these methods among preschool teachers.