For　a　graph　G　and　a　positive　integer　k,　a　k-list　assignment　of　G　is　a　function　L　on　the　vertices　of　G　such　that　for　each　vertex　v　∈　V(G),　|L(v)|　≥　k.　Let　s　be　a　nonnegative　integer.　Then　L　is　a　(k,k+s)-list　assignment　of　G　if　|L(u)∪L(v)|≥k+s　for　each　edge　uv.　If　for　each　(k,k+s)-list　assignment　L　of　G,　G　admits　a　proper　coloring　φ　such　that　φ(v)　∈　L(v)　for　each　v　∈　V(G),　then　we　say　G　is　(k,k+s)-choosable.　This　refinement　of　choosability　is　called　choosability　with　union　separation　by　Kumbhat,　Moss　and　Stolee,　who　showed　that　all　planar　graphs　are　(3,　11)-choosable.　In　this　paper,　we　prove　that　every　planar　graph　without　cycles　of　length　4　is　(3,6)-choosable.　©　2020