title: Understanding the gas and dust structure of protoplanetary disks: a synergy of multi-instrument observations and advanced modeling, the case of HD 135344B authors: A. Carmona, C. Pinte, W.F. Thi, F. Menard abstract: Protoplanetary disks are composed by gas and dust. They display a gradient of temperature and density as a function of the radius and height. In consequence, to probe the disk, multi-wavelength/multi-instrument observations of gas and dust are required. To derive in a coherent way the disk structure from a diversity of diagnostics, thermo-chemical radiative transfer disk models are needed. In this contribution, we present a study that we are carrying on HD 135344B, a well known Herbig Fe star which displays a gap in its disk. We used the radiative transfer codes MCFOST and ProDiMo, to derive the disk structure of HD 135344B by modeling simultaneously the SED, IRS-Spitzer spectra, VLTI-PIONIER near-IR interferometry data, VLT-CRIRES CO 4.7 micron spectra, Herschel [OI] 63 micron emission, and JCMT CO J=3-2 spectra. We describe the disk emitting regions of each tracer and how a diversity of multi-instrument data is used to break model degeneracies.