We now consider acetylene, a linear system with degenerate 1 ∆ u excited states at its groundstate equilibrium geometry. We consider the four lowest valence excited singlet states of acetylene as a function of one of the C-C-H bond angles (defined to be θ where θ = 180 • is the linear geometry (the other C-C-H angle is kept linear). An introduction to the energetics, and Ventura et al. The symmetries of these states for planar, nonlinear geometries are 1 A ′ , 1 A ′′ , 1 A ′ , and 1 A ′′ , in order of increasing energy. For linear geometries, they become 1 Σ + g , 1 Σ - u , and two components of a 1 ∆ u state. Our goal here is to test the accuracy of L-PDFT on this system for which CMS-PDFT is known to provide an incorrect description of the degenerate 1 ∆ u states at θ = 180 • .