The massive production of educational software and easy Internet access to digital resources does not necessarily imply their didactical quality. Based on the theoretical analysis of current research studies about values of technology-enhanced resources for teaching and learning mathematics, the chapter aims at suggesting criteria and an operational definition of the quality of task designs as one type of digital resources and their significance for mathematics education. Furthermore, it explores how this definition arose from previously carefully selected task designs in four specific resources as apps for mobile devices and audio-podcasts for primary school, dynamic geometry software for lower and spreadsheets for upper secondary school.