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Treatment modalities are becoming more and more complex in order to enable advanced patient treatments with a higher dose to the tumor while sparing the organs at risk. The last couple of years a lot of new treatment techniques and modalities became commercially available such as Intensity modulated radiotherapy (IMRT), Helical Tomotherapy, gated treatments, tumor tracking, VMAT, RapidArc, IMAT, dynamic delivery techniques (leafs, gantry and couch), flatness filter free (FFF) designs, etc.. Although the compliance rate for beam calibration is improving and near 98% for both photon and electron beams, increasing treatment complexity leads to more technically advanced components in the treatment chain, possibly inducing discrepancies. Credential audit results from the Radiological Physics Center (RPC) indicate that roughly 30% of the institutions failed to deliver an IMRT dose distribution to a head and neck phantom that agrees with their own treatment plan to within 7% or 4mm. So, even though the use of advanced dosimetry equipment for QA is wide spread, it seams that a lot of caveats are still present in the QA chain of advanced treatment techniques. The choice of a specific QA system depends on the number of treatment parameters to be verified and the extensiveness of the desired QA process. For this choice the use of the conceptual pyramid was proposed by De Wagter et al. In this conceptual pyramid the treatment chain is divided into 4 levels of specificity, all based on the stability of the underlying levels. On top of the pyramid (level 4) we can find the 3D dosimetry of the entire treatment delivery. Descending brings us to level 3 where we find the 1D-2D dosimetry of individual beam components. Level 2 is the planning system and data consistency QA level and at the ground level (level 1) we find the machine QA level.The best way to use the conceptual pyramid is the top down approach where a 3D dosimetry of the entire treatment is delivered to a phantom. When the results show discrepancies, lower levels of the pyramid should be sought to find answers. 3D dose distributions are QA’ed using different types of dosimeters such as; film (EDR2 and EBT2), diode arrays, ionization chamber arrays, EPID detectors, MVCT imaging detectors, etc... Is this talk we will try to give a general overview of dosimetry techniques used to QA 3D dose distributions and we will try to answer some questions: What techniques are used and are the QA tools keeping up with the rapid evolutions of the treatment machine manufacturers ? How are they applied in the different levels of the conceptual pyramid ? Is 3D really 3D ? Where do they stand compared to the ’ideal’ dosimeter ? What are the pros and cons of each group of dosimeters ? How do they fit in the workflow ?