Bipolar disorder looks different in children than it does in adults.
Children with bipolar disorder usually have an ongoing, continuous
mood disturbance that is a mix of mania and depression.
This rapid and severe cycling between moods produces chronic irritability
and few clear periods of wellness between episodes.
Symptoms of bipolar disorder in children may include some
or most of the following:

an expansive or irritable mood
depression
rapidly changing moods lasting a few hours to a few days
explosive, lengthy, and often destructive rages
separation anxiety
defiance of authority
hyperactivity, agitation, and distractibility
sleeping too little or too much
bed wetting and night terrors
strong and frequent cravings, often for carbohydrates and sweets
excessive involvement in multiple projects and activities
impaired or poor judgment, impulsivity, racing thoughts, and pressure to keep talking
dare-devil behaviors and/or grandiose belief in own abilities
inappropriate or precocious sexual behavior
delusions and hallucinations
talk of death or suicide
pervasive sadness and crying spells

In Teens:
In adolescents, bipolar disorder may resemble the classical adult presentations of the illness.
Type I — the adolescent experiences alternating episodes of intense and sometimes
psychotic mania and depression, exhibiting many of the symptoms listed above.
Periods of relative or complete wellness usually occur between the episodes.
Type II — the adolescent experiences episodes of hypomania between recurrent
periods of depression. Hypomania is a markedly elevated or irritable mood
accompanied by increased physical and mental energy.
Cyclothymia — a milder form of bipolar disorder,
the adolescent experiences periods of less severe, but definite, mood swings.

Source:Child & Adolescent Bipolar Foundation

Attention Deficit Disorder (ADD)

A syndrome which is usually characterized by serious and
persistent difficulties resulting in:
Poor attention span
Weak impulse control
Hyperactivity (not in all cases)
ADD also has a subtype which includes hyperactivity (ADHD).
It is a treatable but not curable complex disorder which
affects approximately 3 to 6 percent of the population
(70% in relatives of ADD children).
Source: One ADD Place

ADHD is usually first diagnosed during the elementary-school years.
In some cases, symptoms continue into adolescence.
A teenager with Attention Deficit/ Hyperactivity Disorder
has problems with paying attention and concentration
and/or with hyperactive and impulsive behavior.
Despite good intentions, a teenager may be unable to listen well,
organize work, and follow directions. Cooperating in sports
and games may be difficult. Acting before thinking can cause
problems with parents, teachers, and friends. These teens may
be restless, fidgety, and unable to sit still.
Attention Deficit/Hyperactivity Disorder occurs more commonly in boys
and symptoms are always present before the age of 7.
Problems related to ADHD appear in multiple areas of a
youngster's life and can be very upsetting to the teen, his/her family,
and people at school. Symptoms of ADHD frequently become less severe
during the late teen years and in young adulthood.

Bipolar Disorder

Bipolar Disorder is a type of mood disorder with marked changes in mood
between extreme elation or happiness and severe depression.
The periods of elation are termed mania. During this phase,
the teenager has an expansive or irritable mood, can become
hyperactive and agitated, can get by with very little or no sleep,
becomes excessively involved in multiple projects and activities,
and has impaired judgment.
A teenager may indulge in risk-taking behaviors, such as sexual promiscuity
and anti-social behaviors actions. Some teenagers in a manic phase may
develop psychotic symptoms (grandiose delusions and hallucinations).
For a description of the depressive phase, see depression.
Bipolar Disorder generally occurs before the age of 30 years and may
first develop during adolescence.
Source: American Academy of Child & Adolescent Psychiatry

A persistent pattern (lasting for at least six months)
of negativistic, hostile, disobedient, and defiant behavior
in a child or adolescent without serious violation of the basic
rights of others.
Symptoms of this disorder may include the following behaviors
when they occur more often than normal for the age group:
losing one's temper
arguing with adults
defying adults or refusing adult requests or rules
deliberately annoying others blaming others for their own mistakes or misbehavior
being touchy or easily annoyed
being angry and resentful
being spiteful or vindictive
swearing or using obscene language
or having a low opinion of oneself.
The person with Oppositional Defiant Disorder
is moody and easily frustrated,
has a low opinion of him or herself, and may abuse drugs.
Source: The Cornell Medical Center