In this paper, we report the gas-phase characterization of two differently substituted amino(iminoarsanes), TmpAs=NSiMe3 and (SiMe2tBu)2NAs=N(SiMe2tBu), by coupling flash vacuum thermolysis (FVT) with UV photoelectron spectroscopy (PES). Quantum chemical calculations, using the DFT method (B3LYP) with the basis set 6-311G(d,p), have also been carried out on the R1As=NR2 unit with R1=H, NH2, N(CH3)2, N(SiH3)2 and R2=H, SiH3, in order to study the effect of substitution on the electronic properties and the thermodynamic stability of the As=N skeleton. Similarities with phosphorus analogues are also discussed.