Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Pentax Q10 and Panasonic ZS8 side-by-side from the front, back and top in their relative dimensions. Pentax Q10 has external dimensions of 102 x 58 x 34 mm (4.02 x 2.28 x 1.34″) and weighs 200 g (0.44 lb / 7.05 oz) (including batteries). Panasonic ZS8 has external dimensions of 105 x 58 x 33 mm (4.13 x 2.28 x 1.3″) and weighs 210 g (0.46 lb / 7.41 oz) (including batteries).
Below you can see the front view size comparison of Pentax Q10 and Panasonic ZS8. As you can tell, actually this is not a fair size comparison since Panasonic ZS8 has a built-in lens but Pentax Q10 doesn't. Once you put a lens on Q10, its thickness will increase significantly.
Here is the back view size comparison of Pentax Q10 and Panasonic ZS8.
Now lets look at the top view comparison of Pentax Q10 and Panasonic ZS8.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Pentax Q10 is 10g lighter than the Panasonic ZS8 but we don't think this will make a significant difference.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on Q10, the total kit will weigh much higher.
Unfortunately neither Pentax Q10 nor Panasonic Lumix DMC-ZS8 (Lumix DMC-TZ18) provides any type of weather sealing in their body, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Mirrorless Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Pentax Q10 and Panasonic ZS8's LCD screens has the same diagonal size of 3".
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.