For reinforced concrete structures, as beams, slabs or walls, failure under bending is well known and its description and design is relatively internationally agreed. However for the shear failure phenomenon, there is not yet a common agreement at the international level, no consensus is reached on the subject at this time. Many parameters are involved in the shear resistance mechanism and many phenomena coexist. The shear force transfer mechanisms are sometimes complex and difficult to discern. By analyzing the different shear design codes, some shear parameters are taken into account and ignored by others, which makes that a shear effect may be omitted. In addition, different ways are adopted to take into account the different shear parameters. The main purpose of this study is to help the engineering by presenting a comparative study of all the main analytical models for the determination of shear capacity: The EN 1992–1–1:2005 standard (EC2) (CEN, 2005), French National Annex (FD P 18–717, 2013), ACI 318–14 (ACI Committee 318, 2014), fib Model Code 2010 (Fib Model Code 2010, 2012) using level of approximation LoA I and LoA II and (CSA Committee A23.3, 2004) both Modified Compression Field Theory (MCFT) based models, and finally the Critical Shear Crack Theory (CSCT) which is the basis of the Swiss standard SIA 262 (SIA 262, 2003) are all examined. The results obtained are discussed regarding their agreement with eighteen shear experimental results on thick slabs (30 cm, 35 cm, and 40 cm) and thin slabs (10 cm) without shear reinforcement.