In this study we sought to investigate the development of modeling ability and conceptual understanding about ecosystems of preschoolers (ages 5-6) through the use of a computer tool (Stagecast Creator) and a Role Playing Game. Twenty six preschoolers were assigned in two experimental groups; the first experimental group (n=13) was engaged in modelling activities through the use of Stagecast Creator, whereas the second experimental group (n=13) was engaged in modelling activities with the use of a Role Playing Game as a modelling medium. The context in both implementations was a snail's ecosystem. Semi-structure interviews were implemented both prior to and after instruction to assess students' modelling ability and conceptual understanding about ecosystems. The data collected through the interviews were recorded and transcribed and were analysed with the use of phenomenography. The findings of the study indicate that the students in both groups developed their modelling ability and, at the same time, they improved their understanding about concepts related to ecosystems.