diff --git a/mc-mark-more.el b/mc-mark-more.el
index 7e240a1..26bbe6f 100644
--- a/mc-mark-more.el
+++ b/mc-mark-more.el
@@ -416,6 +416,22 @@ With prefix, it behaves the same as original `mc/mark-all-like-this'"
         (when (<= (mc/num-cursors) before)
           (mc/mark-all-like-this))))))
 
+(defun mc/mark-all-dwim (arg)
+  "Tries even harder to guess what you want to mark all of.
+
+If the region is active and spans multiple lines, it will behave
+as if `mc/mark-all-in-region'. Otherwise, it will delegate to
+`mc/mark-all-like-this-dwim' or `mc/mark-all-like-this' (if the
+prefix ARG is present)"
+  (interactive "P")
+  (if (and (use-region-p)
+           (not (= (line-number-at-pos (region-beginning))
+                   (line-number-at-pos (region-end)))))
+      (call-interactively 'mc/mark-all-in-region)
+    (progn
+      (setq this-command 'mc/mark-all-like-this-dwim)
+      (mc/mark-all-like-this-dwim arg))))
+
 (defun mc--in-defun ()
   (bounds-of-thing-at-point 'defun))
 
diff --git a/multiple-cursors-core.el b/multiple-cursors-core.el
index d073090..4b30cf9 100644
--- a/multiple-cursors-core.el
+++ b/multiple-cursors-core.el
@@ -573,6 +573,7 @@ for running commands with multiple cursors.")
                                      mc/mark-all-words-like-this-in-defun
                                      mc/mark-all-symbols-like-this-in-defun
                                      mc/mark-all-like-this-dwim
+                                     mc/mark-all-dwim
                                      mc/mark-sgml-tag-pair
                                      mc/insert-numbers
                                      mc/sort-regions