Difference between returning and not returning in recursion

Question

I have written a program to print the Kth node from root of a binary tree.

// PRINT KTH NODE FROM ROOT (FUNCTION 1)
void printKth(node *root, int k){
    if (root == NULL){
        return;
    }
    if (k == 0){
        cout<<root -> data<<" ";
        return;
    }

    printKth(root -> left, k-1);
    printKth(root -> right, k-1);
}

For the below binary tree, The code prints

//          100     
//         /   \
//       80     120
//      /  \
//    40    60
// 
// OUTPUT - 80 120

The above function works fine until I add a return statement in the second and third last lines.

// PRINT KTH NODE FROM ROOT (FUNCTION 2)
void printKth(node *root, int k){
    if (root == NULL){
        return;
    }
    if (k == 0){
        cout<<root -> data<<" ";
        return;
    }

    return printKth(root -> left, k-1);    // ADDED RETURN STATEMENT
    return printKth(root -> right, k-1);   // ADDED RETURN STATEMENT
}

For the below binary tree, The code prints

//          100     
//         /   \
//       80     120
//      /  \
//    40    60
// 
// OUTPUT - 80

I can't understand what's happening when adding the return statement.