Plastic fuel tank with increased deformation stability

Plastic fuel tank comprising an upper wall (1), a lower wall (2), at least one kiss point (21) formed by welding together a multiplicity of contact points of the upper and lower walls and an accessory, characterized in that: - both the upper and lower tank walls show a concave recess (3) in the kiss point area so that the weld of the kiss point is located in between the planes defined by the upper and lower walls respectively - the bottom of the upper concave recess (3') extends substantially beyond the weld of the kiss point, while the bottom of the lower one (2') does not - the accessory is at least partially located under the extension of the bottom of the upper concave recess. The invention further comprises a process for manufacturing such a fuel tank.