Hi all
I have an image on a transparent background that I am able to create a drop shadow for (however quality of the shadow color is very poor). When I draw a box round it and copy and past the subject onto my other piture/ layer the shadow dose not come with it!

Any ideas on a fix please

Could have done with more info, version of Gimp, type of image..

Nothing I can do about your perception of quality. The displacement and opacity all depends on the values entered in the tool.

Then the quote "When I draw a box around it and copy paste ....." There are two options once the selection is made.

Edit -> Copy shortcut ctrl-c which copies whatever is on the layer

Edit -> Copy Visible shortcut shift-ctrl -c which does what it says.

If you have the subject on a transparent layer, no real need to make a selection, just copy(or copy -visible) and paste the active layer.

Without more info, best guess, using Gimp 2.10 (although could be Gimp 2.8 for the second case)

Gimp 2.10 has two drop shadow plugins.

The GEGL plugin applies the effect directly on the canvas. see screenshot 1 One layer copy / paste it

The legacy (Gimp 2.8) plugin makes 2 layers see: screenshot 2 Either Layer -> Merge down the two layers into one and copy/paste or use Copy Visible.

That gets you a 'floating selection' screenshot 3. Two options, anchor the layer, which merges down or better, promote to a new layer Layer -> New Layer, which will allow a bit of tweaking.