Cognitive diagnostic models (CDM) have been around for more than a decade but their application is far from widespread for mainly two reasons: (1) CDMs are novel, as compared to traditional IRT models. Consequently, many researchers lack familiarity with them and their properties, and (2) Software programs doing CDMs have been expensive and not readily available. The present paper presents a reader-friendly introduction to the CDMs and uses the CDM package (Robitzsch, Kiefer, Cathrice George, & Uenlue, 2014) in R to demonstrate the application of the generalized deterministic-input, noisy-and-gate model (G-DINA; de la Torre, 2011) and interpret the output. R is a free open source tool which can be utilized to conduct a range of CDMs which otherwise would need separate software programs to run each.